The access of distributed renewable energy enhances the uncertainty of the distribution network reliability, whereas the distribution network reliability evaluation using existing methods cannot fully reflect the stochastic volatility of islanding power supply and loads. For this reason the approach of active distribution network probabilistic reliability evaluation based on point estimation method was proposed. In the framework of Monte Carlo simulation, the islanding random variable was sampled and processed firstly; then the islanding probabilistic reliability was assessed with a nonlinear transformation method of independent random variables based on point estimate method; finally, system probabilistic reliability indexes can be obtained from the probabilistic superimposing of the results of repeating simulated failures. The simulation on the transformed multi-branch feeder model of the IEEE RBTS Bus6 verifies the validity and accuracy of this assessment approach.