The invention relates to a centrifugal water pump, belonging to the hydraulic technical field. The centrifugal water pump comprises a transmission shaft, a bearing, a fastening piece, a bearing seat, a volute, an inlet water pan, an impeller and a mechanical seal. The impeller consists of long blades and short blades. Five long blades and five short blades are arranged in a spacing way. The diameter of the middle shaft hole of the impeller is 18mm, the diameter of a hub is 24mm, the outer diameter of the impeller is 133.6mm, the length of each long blade is 46.8mm, the length of each short blade is 26.8mm, the diameter of the inlet of the long blade and the short blade is 66mm, the setting angle of the inlet of the long blade and the short blade is 36 degrees, the height of the inlet of the long blade and the short blade is 17mm, the thickness of the long blade and the short blade is 3.5mm, the setting angle of the outlet of the long blade and the short blade is 45 degrees and the height of the outlet of the long blade and the short blade is 10.3mm. The runner of the volute is matched with the impeller. The taper of the suction chamber of the inlet water pan is 12.5 degrees. The invention has the advantages of high efficiency, energy saving, good workability, light weight and small volume.