The utility model discloses a hydrolysis -acidification pool with return sludge hole, including hydrolysis -acidification pool, hydrolysis -acidification pool comprises A pond and B pond, is equipped with the partition wall in A pond and the B pond, is equipped with the pavement between A pond and the B pond, and the pavement has a return sludge hole, and the entry in the return sludge hole perhaps exports and is equipped with movable gate and dives the agitator, the return sludge hole site flows in the front end partition wall of direction and the rear end partition wall department of B pond outflow direction in the A pond, compared with the prior art, the utility model has the advantages of as follows: (1 )Improve waste water biodegradability: can turn into the micro molecule with the macromolecule organic matter, (2 )Dissolved oxygen DO among the effectual reduction hydrolysis -acidification pool improves the muddy water mixing ratio, and then improves hydrolytic acidification's effect, (3 )Adopt the dive agitator, prevent effectively that the dead angle department mud among the hydrolysis -acidification pool from piling up, realize the intensive mixing of mud and waste water, (4 )Carry out pulsed work through the dive agitator, carry out return sludge with continuouslying, the oxido reduction potential value control to be in 300 ~ 100 mv accords with the optimal value of water treatment, (5 )The cooperation of filler and partition wall improves a membrane effect and the water conservancy condition of hanging, (6 )The soakage of the area control mud negative pressure through gate opening, the real -time regulation.