A precision four-degree-of-freedom measurement system has been developed for simultaneous measurement of four motion errors of a linear stage, which include straightness and angular errors, The system employs a retro-reflector to detect the straightness errors and a plane mirror to detect the angular errors. A common-path compensation method for laser beam drift is put forward, and the experimental results show that the influences of beam drift on four motion errors can be reduced simultaneously. In comparison with the API 5D laser measuring system, the accuracy for straightness measurement is about ${pm}1.5{mu}m$ within the measuring range of ${pm}650{mu}m$, and the accuracy for pitch and yaw measurements is about ${pm}1.5$ arc-seconds within the range of ${pm}600$ arc-seconds.