The invention provides a regulation storage tank containing a water passing groove. The water passing groove is located at the upper portion of the regulation storage tank, wall bodies on the two sides of the water passing groove are higher than the highest water storage level of the regulation storage tank, one end of the water passing groove is connected with a water inlet pipe of the regulationstorage tank, and one end of the water passing groove is connected with a pipe leading to a sewage treatment plant. A water-passing-groove overflowing water inlet structure is used in the regulationstorage tank, the occupied area of a water inlet area is small, and the land shortage condition of some areas can be relived. A structure with the slope-shape bottom is also used in the regulation storage tank, and the condition that a large area of silt is precipitated at the bottom of the regulation storage tank can be prevented. In addition, regulated-stored mixed sewage can also be stirred andaerated through a washing device, and when the to-be-regulated-stored water level is low, the bottom is washed, and the tank bottom is kept clean.