During the reign of Emperor Yao, there was an enormous flood in the Basin of the Yellow River. During the flood, crops were submerged, houses destroyed, and humans as well as livestock attacked by vipers and aggressive beasts. People led a hard life.

Under such a circumstance, Emperor Yao held a meeting of the tribal alliance to discuss the water-control problem. Leaders of all tribes suggested that Gun be sent to control the flood. However, nine years of Gun's efforts turned out a failure. He knew nothing but halted water with earth and built dams. Later the dam was inundated, giving rise to a fiercer flood.

After Shun succeeded to Emperor Yao as the leader of the tribal alliance, he killed Gun on the ground for Gun failed to fulfill his task. Then Shun sent Yu, Gun's son, to control the flood. Different from his father, Yu drained water through ditches, and dredged the riverway. Eventually, he succeeded in channeling the flood into the sea.

At that time, there was a huge mountain in the middle reaches of the Yellow River, which was called Longmen Mountain (now the northwest of Hejin County in Shanxi Province). It blocked the water and narrowed the riverway, thus frequently resulting in floods. After Yu got there, he closely examined the terrain and then led people in excavating Longmen Mountain. When an enormous opening was excavated in the mountain, the water managed to flow without obstacles.

In praise of Yu's achievements in flood control, people of later generations respectfully entitled him with Dayu, meaning Great Yu.