Xu was a close friend of Cao Cao and during the Battle of Guandu, Xu decided to leave Yuan Shao and join Cao. This was because Shen Pei had informed Yuan that Xu's family had been locked up for charges of corruption. At that time, Xu was suggesting a strategy to Yuan and when Yuan received the news, he sneered at Xu and said, "You still have the cheek to present your strategies in front of me."
Xu was furious and left Yuan to join Cao. He suggested that Cao attack Wuchao, where Yuan's army had their supplies stored. It was due to Xu's plan that Cao managed to win a strategic victory over Yuan's massive army in the Battle of Guandu. Later, Xu showed disrespect when Cao paid his respects in front of Yuan's grave, and was killed by Xu Chu.