Abstract: Through the comparison investigation of spread spectrum and scrambling code between CDMA2000 and TD-SCDMA (TD), an equivalent scheme of spread spectrum and scrambling code for TD is presented firstly. The equivalent scheme indicates that the basic principle of the spread spectrum and scrambling code of the two schemes，CDMA2000 and TD，is identical in nature. The equivalent scheme also shows that in TD system each path signal from QPSK modulator is transmitted with 3-level, which results in loss in power efficiency. Since in the 3-level signal transmission half of the transmitted data are zero, there are one half of the transmitting power can not be used effectively. At the same time, in contrast to CDMA2000 and WCDMA, TD hasn’t the 1+1 backup function originated from orthogonal diversity transmission, which results in the decrease of the system stability. Thus, we present a modified scheme of spread spectrum and scrambling code for TD-SCDMA (MSS-TD) as well as the comparison analysis of system performance. The proposed scheme integrates the merits of the both schemes, CDMA2000 and WCDMA. The theory deduction and simulation analysis show that MSS-TD improves the system performance, such as signal-to-noise ratio (SNR), bit error ratio (BER), etc. The improvements are more remarkable when the interferences of neighborhood sectors are considered specially.