A method for generating chaotic spread-spectrum sequences based on the combined chaotic map is proposed. An optimized selection algorithm based on the property requirement of spread-spectrum sequences and the performance index of multiple access interference is also presented. Simulation is performed for the optimized chaotic sequence, and an optimized logistic sequence is applied to a direct sequence spread-spectrum CDMA system under different channel conditions. The results show that the chaotic spread-spectrum sequences generated by the proposed method have similar performance as the logistic spread-spectrum sequences and have better security.