Yu Baosi has a big and tall stature. He is nicknamed "God of the Dangerous Road" for his gigantic build. He used to lead a group of about 200 bandits and they rob travellers on the roads in Qingzhou. Yu Baosi becomes the chief flag bearer of Liangshan for his big stature after the Grand Assembly of the 108 Stars of Destiny. Finally, He is slain by the enemy officer Du Wei at the battle of Qingxi County during the campaign against the rebel leader Fang La.