The shortcomings of the submerged dredge pump of 400 m3/h cutter suction dredgers are pointed out based on researching its suction capacity;technical innovations are carried out to submerged dredge pump of 400 m3/h cutter suction dredgers by two pumps in series;so that it satisfies a dredging depth of 18 m,spoiling distance of 3 000 m and dredging capacity of 1 250 m3/h.