A two-degree-of-freedom (2-DOF) error measurement system is proposed for assessing the positioning errors of a rotary stage. Additionally, this study introduces a compensation method for addressing four-degree-of-freedom (4-DOF) laser drift errors and presents a refined approach for correcting the decoupling matrix. Initially, passive compensation is utilized to address the 4-DOF laser drift errors, and the impact of laser drifts is minimized through an averaging technique. Subsequently, the identified laser drift errors are analyzed using a mathematical model to effectively compensate for these errors and enhance the overall accuracy of the measurement system. Concerning the correction of the decoupling matrix, a more precise method is employed in contrast to traditional approaches. Experimental data obtained from commercial interferometers are subjected to linear fitting using the least squares method, facilitating a more accurate refinement of the decoupling matrix. This method enables a better alignment of the decoupling matrix with the experimental conditions.