The invention discloses a hydraulic pressure engine based on a reversing valve. The hydraulic pressure engine comprises the reversing valve, an engine body, a transmission assembly, a water inlet pipe, a water draining pipe and a communicating pipe; the reversing valve comprises a shell and a valve core; the valve core is rotatably mounted in an inner cavity of the shell in a sealing mode, and thevalve core makes the reversing valve switch between the two states of water inlet and water draining through rotating; the engine body comprises a cylinder body, a piston, a connecting rod and a crankshaft; the transmission assembly is used for transmitting power from the crankshaft of the engine body to the valve core of the reversing valve; the water inlet pipe communicates with a water inlet of the reversing valve; the water draining pipe communicates with a water outlet B of the reversing valve; and one end of the communicating pipe communicates with a water outlet A and a water return port of the reversing valve, and the other end of the communicating pipe communicates with a water port of the engine body. According to the hydraulic pressure engine based on the reversing valve, kinetic energy of water is converted into mechanical energy, the structure of the hydraulic engine is simple and small, power output is stable and reliable, the energy conversion efficiency is high, and the hydraulic engine can be used for being connected to other power devices for doing work.