International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper analyzes the performance of an M-ary spread spectrum system with orthogonal codes. A new scheme of M-ary spread spectrum communication with phase shifted msequence is proposed, and the method to implement code synchronization in the scheme is given. The performance of the new scheme is analyzed, and compared to conventional spread spectrum systems and orthogonal code M-ary systems. The results show that stronger anti-interference ability, and better data transmission efficiency, and lower complexity is achieved in the system employing phase shifted m-sequence.