To improve the multiple access performance of Transform Domain Communication System, and reduce the bit error rate of system, SPC-TDCS (Spread Phase Coding based TDCS) is proposed based on modified Logistic chaotic sequence. Taking modified Logistic chaotic sequence as a spread sequence in accordance with the principle of the optimized sequence, the random phase vector generated by m sequence is utilized by phase encoding vector to form spread random phase vector (SRPV). The simulation results show that the spread basic function has still more randomness, and the generated SRPV is superior in relative performance to the traditional random phase vector. No matter in the condition of singleuser or multiusers, the spread basic function based on modified Logistic chaotic sequence (SBFML) has an improved gained SNR, and its performance is better than that of the traditional basic function and the spread basic function based Gold sequence. By doing so, this significantly enhances antijamming capability and realizes further TDCS multiple access capability.