Abstract: The satellite communication systems can be jammed by passive intermodulation (PIM) interference signals，and the transmission channel may be blocked at worst. In order to analyze the performance of peudonoise (PN) code acquisition with the passive intermodulation interference quantitatively，the model of direct sequence spread spectrum (DSSS) systems with interference was established. The common methods of PN code acquisition were square law detection and square accumulation detection. The modified Cauchy distribution model was proposed to describe the statistical property of PIM. In consideration of PIM and the receiver noise，the acquisition performances of both detection methods were derived and simulated. The simulation results show that in the case of high signal to interference plus noise ratio(SINR)，the noise has a worse effect on PN acquisition performance than PIM. When the detection probability is 90%，the difference is 2.92dB. The performance of detection method with accumulation is better than that without accumulation，and achieves an accumulation gain. When the detection probability is 90%，the accumulation gain is 2.36dB.

Key words: passive intermodulation, direct sequence spread spectrum system, peudonoise code acquisition, modified Cauchy distribution, acquisition detection probability