The work aims to study find ways to reduce abrasive wear, grinding heat and lower the surface roughness of the workpiece from grinding fluid pressure and lubrication. This article based on the actual situation,The abrasive particle distribution function and the roughness function of the workpiece before grinding are equivalent to the cosine function, When the ceramic bonded CBN grinding wheel grinding No. 45 steel,the fluid pressure and film thickness are analyzed . The results show that considering the surface roughness of the grinding wheel and the workpiece, the pressure fluctuation is concentrated in the central area, the maximum pressure and the maximum thickness of the grinding area obviously increased. In the case of thermal effects: When the wavelength of two surfaces are equal and the amplitude of two surfaces increases simultaneously, the maximum film thickness and average film thickness increases. When the amplitude of two surfaces are equal and the wavelength of two surfaces increases simultaneously, the lubrication does not improve. When he amplitude of the grinding wheel surface is equal to the wavelength and increase simultaneously, the maximum film thickness and average film thickness increases, which can also be obtained when the wheel surface amplitude and wavelength constant, the workpiece surface change the same situation; when the two surface amplitude and wavelength are not equal and multiplied , the maximum film thickness and average film thickness increases to, the above three conditions, the increased film thickness which conducive to lubrication can lower the grinding temperature, reduce grinding burns ,thermal deformation and the workpiece roughness after grinding. It also can reduce the wear of non-working abrasive grains and the number of grinding wheel correction to extend the wheel life. But the film thickness will not increase indefinitely, because the grinding area is not closed, but the optimal solution can be based on this theory in the actual project to optimize the grinding process.