The invention discloses an adjustable water suction pump which comprises an outer shell and a motor. An inlet connecting pipe is arranged on one side of the outer shell. An inlet check valve is installed at one end of the inlet connecting pipe. A water adding valve is arranged at one end of the inlet check valve. A speed governor is installed at one end of the motor. A programmable logic controller (PLC) is arranged on the lateral wall of the speed governor. An impeller is installed at one end of the speed governor. A sealing ring is installed between the impeller and the speed governor. A flow counter is installed inside the outer shell. A sealing cover is arranged on one side of the impeller. An outlet connecting pipe is installed on the lateral wall of the outer shell. One end of the outlet connecting pipe is connected with a gas-liquid separation pipe. The adjustable water suction pump is suitable for not only a river embankment but also an urban street, a doorway, an underground passage opening, a building and the like, can be used for flood control over the river embankment, can automatically work out the water suction capacity, can adjust the water suction efficiency according to needs, is high in work efficiency and free of influences of environment factors, has good social benefits and economical benefits and is suitable for application and popularization.