波片相位延迟量误差是影响旋转波片法斯托克斯(Stokes)参量测量精度的主要因素。通过对传统旋转波片法测量Stokes参量的原理进行理论分析，研究了测量误差与相位延迟量误差之间关系，提出了提高偏振光Stokes参量测量精度的方法。该方法通过调整检偏器透光轴方向与待测光束偏振方向成90°或45°后再进行测量，可有效减小波片相位延迟量误差对Stokes参量测量的影响。实验结果表明，当相位延迟量误差小于1.2°时，采用所提出的优化旋转波片法使Stokes参量测量误差从传统旋转波片法的4.31%减小到0.33%。

The retardation error is the main error of Stokes parameters measurement based on rotating quarter-wave method. The principle of Stokes parameters measurement based on conventional rotating quarter-wave method is analyzed theoretically. The relation between the retardation error and the measurement error is discussed. An improved rotating quarter-wave method is proposed for improving the measurement accuracy of Stokes parameters. In this method, the angle between the axis of polarizer and the polarization direction of the light is adjusted to a certain value (90° or 45°), and the influence of the retardation error on the measurement accuracy of Stokes parameters is reduced obviously. The effectiveness of the proposed method is investigated by comparing to the conventional rotating quarter-wave method through experiments. Experimental results show that the measurement error of Stokes parameters is reduced by the proposed method from 4.31% to 0.33%, under the condition that the retardation error is lower than 1.2°.