The invention discloses a structure improved sewage sedimentation tank. The structure improved sewage sedimentation tank comprises a sedimentation tank, a plurality of fixed seats are sleeved and fixed on a side wall of the sedimentation tank, guide rails are inserted to the fixed seats, the two guide rails at the upper side of one fixed seat are fixedly connected by a connecting block, a pivot isfixedly inserted on the connecting blocks, guide wheels are sleeved on the pivot, ropes are inserted to the guide wheels, one ends of the ropes are fixed on support seats, the support seats are molded on a horizontal pore plate, the pore plate is hinged to the guide rails, a rotary motor is fixed at the lower sides of the guide rails, a limit plate is inserted to the rotating shaft of the rotarymotor, and the limit plate abuts against the bottom surface of the pore plate. The other ends of the ropes are fixedly wound on a transmission shaft, a plurality of gears are fixedly sleeved on the transmission shaft, racks cooperating with the gears are molded on the guide rails outside the sedimentation tank, the transmission shaft is connected to the rotating shaft of a lifting motor, the lifting motor is fixed on a mounting plate, and the mounting plate is fixed on a piston rod of a shift cylinder. The structure improved sewage sedimentation tank provided by the invention can accelerate the sedimentation of particles and improve the sedimentation efficiency.