Abstract: In the grinding process, hydrodynamic pressure has great influence on flow rate, lubrication and cooling behavior of the coolant lubricate.Based on hydrodynamic lubrication theory, mathematical model of the hydrodynamic pressure in grinding contact zone is built.After simplifying the differential equation into Poisson equation, numerical solution of the hydrodynamic pressure is presented by finite difference method and optimized in efficiency by iterative model.Characteristics of grinding wheel are also considered into the mathematical model based on which the hydrodynamic pressure could be estimated according to the wheel texture, the gap between wheel and workpiece, and the cutting speed.The experimental results correspond to the mathematical results and show that this mathematical model can be used for hydrodynamic pressure prediction and provide reference for the grinding process.