The multi-user random communication system is a new researchful subject. Now most researches focus on fixed assignment multiple access method. A new approach that combine the fixed multiple access technology with the random multiple access technology is proposed in this paper, that is the DS/CDMA-time slot-nonpersistent CSMA access approach. The Markov-Chain mathematics model is set up. And then the transition of channel states is depicted and the formula of the network throughput is found. The factors influencing the performance of the DS/CDMA time-slot nonpersistent CSMA multi-user communication systems have been analyzed by Monte-Carlo simulation. It has been proved that the performance of the communication systems can be improved by using this approach.