讨论了非线性偏振旋转效应对主动锁模光纤环形激光器脉冲成形及稳定性所起的作用。定性分析和实验结果均表明，适当控制腔内非线性偏振旋转，可形成一种特殊状态，在这种状态下，非线性偏振旋转效应同时起到压窄脉冲和改善稳定性的作用。 The effects of nonlinear polarization rotation on pulse shaping and stability of active mode-locked fiber ring lasers are discussed. Qualitative analysis and experimental results show that proper control of the non-linear polarization rotation in the cavity can form a special state in which the non-linear polarization rotation effect plays the role of narrowing the pulse and improving the stability.