All the highways leading to the city, about 450 kilometers away from the provincial capital of Chengdu have been cut off and only several paths available. The streets in the city have been submerged, with the water level as high as the third floor of some buildings.
Water supply has been forced to stop and power cut is experienced in many parts of the city, said an official.
Major government officials have rushed to the flood-hit areas and the armed police are busy evacuating residents to safe places, he added.
Over the past three days, Dazhou has witnessed 461 millimeters of rainfall, the highest in a century.