Locking valve, hydraulic torque converter, transmission system for vehicle and vehicle

The invention provides a locking valve, a hydraulic torque converter, a transmission system for a vehicle and the vehicle. The locking valve is provided with an oil inlet port, an oil return port and a working port and comprises an oil supply adjusting valve and a buffer control portion, wherein the oil supply adjusting valve is provided with a first working position and a second working position, the working port communicates with the oil return port and disconnected with the oil inlet port at the first working position of the oil supply adjusting valve, and the working port communicates with the oil inlet port and disconnected with the oil return port at the second working position of the oil supply adjusting valve; and the buffer control portion is configured to control the oil supply adjusting valve to be switched between the first working position and the second working position, and in the process that the oil supply adjusting valve is switched from the first working position to the second working posit