In order to reduce the nonlinear error of the heterodyne interferometer, a polarization-maintaining retroreflector is used in a plane mirror heterodyne interferometer instead of a corner prism due to its defects. According to the basic optical path diagram of the plane mirror heterodyne interferometer, based on the basic optical characteristics of the polarization beam splitter and the corner cube, the effects of the yaw angle, the pitch angle and the rolling angle of the three polarization beam splitters in the plane mirror heterodyne interferometer, and the spacing and angle between the two polarization beam splitters in the polarization-maintaining retroreflector, and the yaw angle and pitch angle of the corner prism on the interferometer were analyzed. The maximum installation error of each optical component in the heterodyne interferometer is deduced, and its machining precision is specified to ensure the performance of the heterodyne interferometer.