对非线性单模光纤法布里珀罗腔的衰荡效应进行理论研究，导出非线性单模光纤法布里珀罗腔输出光场与光纤非线性相移之间关系的数学表达式。结果表明，非线性单模光纤法布里珀罗腔的输出特性包含振荡建立、饱和与衰荡三部分，输出信号功率随腔内信号功率的增大而减少，当腔内信号光功率超过2 W时，输出信号达到稳定的时间变长，并出现不稳定性，但对衰荡时间的影响不大，与在不考虑光纤非线性相移时的线性单模光纤法布里珀罗腔的实验结果一致，所得结果对非线性单模光纤法布里珀罗腔的实验研究具有指导意义。

Cavity ring-down(CRD) in a nonlinear single-mode fiber Fabry-Pérot (F-P) cavity is researched theoretically, and expression of the relation between output electric field amplitude and nonlinear phase shift is derived. Numerical results demonstrate that the output performance of nonlinear single-mode fiber Fabry-Pérot cavity includes three phases: build-up, stability, and ring-down phase. Output power is inversely proportional to the power in cavity. When the power in cavity is larger than 2 W, the stable time for output signal with instability becomes longer, but the effect of self-phase modulation on CRD time is ignoring. It′s consistent with the experimental results of linear single-mode fiber Fabry-Pérot cavity when the nonlinear phase shift is not included. The obtained results have theoretical guidance to the experimental research of nonlinear single-mode fiber Fabry-Pérot cavity.