A hydrodynamic suspension machining system based on digital machine tool was constructed,and a compliant machining apparatus for controlling mechining pressure was developed.Fluid pressure distribution in the machining clearance was analyzed by hydrodynamic theory.An experiment was carried out to obtain influence of machining clearance and motor rotate speed on fluid pressure.Meanwhile,the correlation between the surface roughness of machining clearance and motor rotate speed was revealed by conducting experiments.The experimental results indicate that the fluid pressure increases gradually with increasing of motor rotate speed and decreasing of machining clearance,and then,it decreases relatively after reaching a certain value.When the motor rotate speed is 6 000 r/min,the hydrodynamic pressure shows the maximum value.It also indicates that when the machining clearance is between 5 μm and 40 μm,the machining shows an effect distinctly.In the condition of maintaining clearance of 10 μm and hydrodynamic pressure of 5 N,the machining effect is optimal.