Abstract: Passive intermodulation interference is a thorny problem faced by satellite communication and mobile communication. Both the basic research and engineering application of passive intermodulation effect cannot be separated from passive intermodulation test. Passive intermodulation test error is closely related to carrier power accuracy, residual passive intermodulation level of test system, receiver detection accuracy and other factors. However, the existing passive intermodulation error evaluation methods only consider the upper and lower limits of the error, without considering the error distribution characteristics. Based on the theory of signal vector synthesis and Monte Carlo simulation, this paper studies the distribution characteristics of passive intermodulation test error, and carries out preliminary experimental verification. The theoretical and experimental results show that when the intermodulation level to be measured is close to the residual intermodulation level of the system, the passive intermodulation test error has an asymmetric distribution characteristic, and the probability of positive error is large; When the intermodulation level to be measured is significantly higher than the residual intermodulation level, the error distribution shows symmetry, and the probability of positive error and negative error is about equal. The research results can be used for reference in the fine evaluation of passive intermodulation test results.