The 3D model of Ngau-Tau-type EDM machine was established by SolidWorks software.Then finite element analysis was carried out by ANSYS Workbench software.The results show that ram,Z-axis,and Z-axis base are the major parts of the distortion.The deformation is increased with the upward movement of Z-axis.The counterweight to Z-axis is not only beneficial to reduce motor load,improve the bearing capacity and motion sensitivity of the machine tool,but also good for reducing the deformation.