Guo Tu was a native of Yingchuan. Xun Yu's younger brother Xun Chen, as well as Xin Ping and Guo Tu, who came from the same commandery as Xun Yu, were all employed by Yuan Shao. When Guo Jia first went north and met Yuan Shao, he told Yuan Shao's advisers Xin Ping and Guo Tu that Lord Yuan took up many lines of business but grasped few essentials, and loved scheming but lacked decision, so it would be hard to settle the enterprise of a king or hegemon with him, and he left. Records, Wei 6 §48Records, Wei 10 §4Records, Wei 14 §31
The enthronement of the Son of Heaven had not been Yuan Shao's wish in the first place. When the Son of Heaven was in Hedong, Yuan Shao sent Guo Tu of Yingchuan as his envoy, and on his return Guo Tu urged Yuan Shao to welcome the Son of Heaven and make Ye the capital, but Yuan Shao did not follow his advice. Just then Taizu (Cao Cao) welcomed the Son of Heaven, made Xu the capital and took the lands south of the Yellow River, and all of Guanzhong submitted to him. Yuan Shao regretted it and wanted Taizu to move the Son of Heaven to Juancheng so as to have him near, but Taizu refused. Records, Wei 6 §48
In the 2nd month of the 5th year of Jian'an (200), Yuan Shao sent Guo Tu, Chunyu Qiong and Yan Liang to attack Liu Yan, Administrator of Dong Commandery, at Baima, while he himself led his troops to Liyang, intending to cross the Yellow River. In the 4th month Taizu came north to relieve Liu Yan, beheaded Yan Liang and lifted the siege of Baima. Records, Wei 1 §60–61
At Guandu, when Yuan Shao had Chunyu Qiong and others supervise the transport of grain and station at Wuchao, Taizu personally launched a swift attack on them. When Zhang He said they must hurry to lead troops to the rescue, Guo Tu said, 'Zhang He's plan is wrong. It would be better to attack his main camp. Then he will be bound to return; this is the way to resolve the matter by itself without a rescue.' Zhang He countered that Lord Cao's camp was strong and could not be taken, but Yuan Shao sent only light cavalry to rescue Chunyu Qiong and attacked Taizu's camp with his main force, and could not take it. Records, Wei 17 §42–43
When Taizu did indeed defeat Chunyu Qiong and the others, Yuan Shao's army collapsed. Guo Tu, ashamed, slandered Zhang He again, saying, 'Zhang He is pleased that our army was defeated and has spoken insolently,' and Zhang He, afraid, at last went over to Taizu. Records, Wei 17 §44
After his defeat at Guandu, Yuan Shao fell ill and died of anxiety in the 7th year of Jian'an (202). Yuan Shao loved his youngest son Yuan Shang and wanted him as his successor but had not yet made it known. Shen Pei and Feng Ji vied for power with Xin Ping and Guo Tu; Shen Pei and Feng Ji sided with Yuan Shang, and Xin Ping and Guo Tu with Yuan Tan. The people wanted to set up Yuan Tan because he was the eldest, but Shen Pei and the others, fearing that if Yuan Tan were set up Xin Ping and the others would harm them, used Yuan Shao's long-held wish as a pretext and set up Yuan Shang. Unable to succeed, Yuan Tan styled himself General of Chariots and Cavalry, and from this a rift arose between the two brothers. Records, Wei 6 §58 · 60
When Taizu defeated Yuan Tan and Yuan Shang in successive battles at Liyang, the generals wanted to press their advantage and attack. Guo Jia said that Yuan Shao had not been able to settle on either of his two sons as heir and that Guo Tu and Feng Ji had become their advisers, so they would surely set the two fighting and the brothers would split apart; he therefore proposed to feign an attack on Jing Province and wait for things to change. When Taizu went south as far as Xiping, Yuan Tan and Yuan Shang at last raised troops and attacked each other. Records, Wei 14 §36Records, Wei 6 §62
While Taizu was besieging Ye, Yuan Tan seized Ganling, Anping, Bohai and Hejian, attacked Yuan Shang at Zhongshan and took over his followers. When Taizu was about to attack Yuan Tan, Yuan Tan abandoned Pingyuan, took in Nanpi as well and stationed himself at Longcou; in the 12th month, when Taizu encamped before his gates, he fled by night to Nanpi and camped by the Qing River. In the 1st month of the 10th year of Jian'an (205), Taizu attacked and took Nanpi and beheaded Yuan Tan, Guo Tu and others. Records, Wei 6 §67
Chen Shou wrote no separate assessment of Guo Tu. In the assessment of Records of Wei 6, he said that Yuan Shao was outwardly magnanimous but inwardly jealous and loved scheming but lacked decision, and that it was no misfortune that his line of succession was toppled after he set aside the eldest son and set up a younger one. Records, Wei 6 §96