DS-CDMA developed on spread spectrum is a multiple access technology, but it is difficult for such a system to attain a satisfactory performance under overloading conditions. A sparse DS-CDMA system is presented. It is possible to represent the relationship between the chips and the users using a low density Tanner graph. By doing so, each user is only connected to limited non-zero chips, which can minimize the multiuser interference. According to graph theory, a belief propagation algorithm, which is suitable to the case of low density graph, was adopted by the sparse DS-CDMA to perform multiuser detection. Thus the negative effect of channel noisy and interference can be eliminated. Computer simulation was done. The theory analysis and simulation results showed that the sparse DS-CDMA can achieve excellent performance even under serious overloading conditions.