Aiming at the different installation positions of hydraulic control one-way valve in hydraulic locking circuit, based on the analysis to the opening necessary conditions and the opening control pressure under different working conditions of hydraulic control one-way valve, the idea was put forward that opening pressure of hydraulic control one-way valve was maximum when the hydraulic oil went into the chamber without rod, backed to the chamber with rod and the hydraulic cylinder subjected to reversed load. The relation between control pressure and the load of the hydraulic cylinder, the relation between structure parameters M of hydraulic control valve, the speed ratio φ of hydraulic cylinder and oil resistance Δp were described. Speed ratio φ of the hydraulic cylinder is bigger, the opening pressure is greater; the structure parameter M of the hydraulic control one-way valve is larger, the opening pressure is smaller.