Abstract: An improved Mary spread spectrum communication algorithm was proposed based on the problem that Mary spread spectrum adopting code phase shift keying (CPSK) needs synchronization information. The scheme is easy to realize because all spread spectrum codes comes from one SS code and its reverse order sequence. The scheme adopts BPSK modulation based on polarity modulation of PN in inphase branch, and CPSK modulation based on phase modulation of PN code in orthogonal branch. The system has the advantages which can achieve carrier synchronization accurately and fleetly, but rather offer additional synchronization resource. The simulation results demonstrate that the algorithm is effective in improving the utilization ratio of system resources.