Passive intermodulation (PIM) has become a threat to high-power and multiple-channel communication systems as self-interference sources. A communication channel model with high-order PIM interference is proposed in this letter. Considering the nonignorable additive white Gaussian noise in communication systems, an extended model for PIM interference based on modified Cauchy and Gaussian mixture distributions is presented. A closed form for bit error rate (BER) is derived based on the statistical model of PIM. The BER performance of the proposed distribution model outperforms the existing analysis methods and approximates the simulated results. This research is of practical significance for communication system design and link margin analysis.