Nonlinear constant r | could be calculated according to the numbers of the diffraction rings . the sample's optical limiting properties were discussed . according to the experimental results, we estimated that the main mechanism of the optical limiting was from the thermo-optic effect 对2-甲氧基5-丁氧基取代ppv氯仿溶液进行了激光诱导自衍射实验,根据衍射环的个数估算出了样品的非线性常数;同时还对该样品进行了光限幅特性的研究,由实验结果分析得出:由光热效应引起的自衍射是产生光限幅特性的主要机制。