Gongsun Zan and Liu Bei have established a good friendship, and this situation continues into adulthood. He used his influence to serve as Governor of Peiping, and Liu Bei was appointed as the county magistrate. When establishing an alliance with Dong Zhuo, Gongsun Zan joined and moved south. During the parade, he passed through the plains and met with Liu Bei to let him recover the Han with him. Liu Bei agreed, and the two continued to go south. When meeting with other lords, Gongsun Zan introduced Liu Bei to others. However, the meeting was interrupted by a messenger who told them that Hua Xiong's advance was moving forward. When some of the lords' generals were killed, Guan Yu challenged him and annoyed Yuan Shao and Yuan Shu. Cao Cao and Gongsun Zan managed to calm them down and Guan Yu killed Hua Xiong. As Yuan Shu was still angry, Gongsun Zan led Liu Bei and his brother to the camp to calm him down.
But later on, Gongsun Zan was one of the seven lords who were sent to fight Lu Bu. When Gongsun Zan praised him, Lu Bu killed many generals. However, Gongsun Zan cannot be compared with him. Lu Bu was able to catch up and lift the strike, Gongsun, but the latter was saved and fled by Zhang Fei. After the dissolution of the alliance with Dong Zhuo, Gongsun Zan received a letter from Yuan Shao asking him to conduct a joint attack on Han Fu in Ji Province. Gongsun Zan agreed, but Yuan Shao secretly met with Han Fu and told him the attack of Gongsun Zan, giving him a joint defense, just to betray Han Fu and seize power for himself. Gongsun Zan sent his brother Gongsun Yue to ask for some of Ji Province, but Yuan Shao refused speak to him and wanted to talk to Gongsun Zan himself. After returning from Gongsun Yue, he was ambushed and killed on the way to the person who claimed to serve Dong Zhuo. Gongsun Zan praised Yuan Shao's war through tricks.
Gongsun Zan and Yuan Shao's powers met in the Pan River, where Gongsun Zan would challenge the enemy General Wen Chou. Gongsun Zan is not suitable for him and quits. Wen Chou went to pursue, Gongsun Zan praise cannot lose him. Wen Chou chased him to the mountains, and Gongsun Zan's praise stopped there and threw him to the ground. If there is no Zhao Yun who came to join him, Gongsun Zan was almost killed. Gongsun Zan and Zhao Yun together killed Yuan Shao's general Qu Yi. Yuan Shao himself was ambushed by Liu Bei and his brother. They came to help Gongsun to escape. Gongsun Zan stopped fighting after receiving a decree from Dong Zhuo and expressed his appreciation to Governor of Pingyuan for his promotion to Liu Bei.
When Liu Bei is try to attack Cao Cao, he asked Gongsun Zan for troops. Gongsun Zan was very concerned and suggested not to attack, but he eventually surrendered and sent 2,000 men and Zhao Yun to support him. Gongsun Zan was caught off guard by Yuan Shao's attack and hid in the Yijing. The siege continued until an officers of Gongsun Zan requested reinforcements. Gongsun Zan denied the reinforcements and thought that if they did not receive any assistance, his people would work harder. This led many of Gongsun Zan's men praises to Yuan Shao and his men, who dug a tunnel and set fire to the city. Gongsun Zan withdrew his tower, where he killed his family and committed suicide. In later, Zhao Yun reported his death to Liu Bei.
- He is famed for his White Riders unit, which are five thousand elite soldiers on white steeds.