Continuous phase modulation spread signal is gradually applied to satellite communication because the spread spectrum sequence changes randomly and can be adapted to multi-user communication. Random access channel of VDE system uses QPSK-CPM spread modulation scheme. A new multiuser detection algorithm based on interference cancellation detection is presented for QPSK-CPM spread spectrum system. The algorithm detects multi-user information by cascaded one-iteration elimination of successive interference cancellation for receiving user information. The algorithm can effectively eliminate the user's doppler frequency offset and reduce the performance loss caused by user power difference. The simulation results show that the new algorithm has better detection performance than the traditional interference cancellation detection algorithm. When the number of real-time communication ships reaches 800, the deframe rate of overlapping information within 8 users can reach 90%.