Proposed in this paper is a new method to evaluate the voltage sag sensitivity (VSS) of the sensitive load by combining several probability density function models,which can fully describe the randomness of the load sen-sitivity.First,five typical probability density functions are deeply analyzed and are used to respectively establish the mathematical model of the voltage tolerance curve of the sensitive load,and the VSS of the sensitive load in the uncertainty region is evaluated respectively by the five models.Then,the weighted sum of the results of the fivemodels is calculated by means of the unbiased variance method.Finally,the rationality and effectiveness of the pro-posed method are verified by simulation results.