Rail grinding is an important method for metro rail maintenance. The rail grinding process is a mechanical, electric, and hydraulic coupling process built on vehicle-track relationship. A low grinding power may result in a low grinding effect, whereas a high grinding power may cause a white layer and damage to the rail. Constant-power grinding is the traditional grinding method, and the grinding effect is constrained by this undifferentiated grinding style. In this study, first, a rail grinding model is established. The goal of this study was to improve the hydraulic system by installing check valves at the oil inlet and outlet. The grinding pressure at the peak of rail irregularity was increased through the delayed pressure relief induced by these valves, and the grinding effect was improved. Normal corrugation allows for the maintenance of the grinding pressure and an improvement in the peak clipping effect. Under severe corrugation, the grinding pressure can be released and the grinding power fluctuation can be narrowed. The difference in corrugation depth before and after grinding under normal corrugation was taken as the objective function. The extreme value of grinding power under severe corrugation is a boundary condition. The cracking pressure of the check valve in the oil outlet was optimised. The optimal cracking pressure of this check valve was analysed in this study using modelling and simulation. The results showed that the optimal cracking pressure for this valve was 60 psi. The grinding effect increased by 12.7% under normal corrugation using this improved technique. Additionally, during severe corrugation, maximum grinding power is 30 kW, which is within the allowable range.