Abstract: As the transmission rate and bandwidth efficiency of tradition direct sequence spread spectrum (DSSS) system are relatively low. Based on the basic characteristics of spread sequences, DSSS modulated signals and the theories of Hilbert transformation, a novel DSSS baseband modulation method is proposed. Theoretical analysis and simulation experiments are carried out on the characteristics of inter branch and intersymbol interference of modulated signal. Results show that under additive white Gaussian noise (AWGN) channel, compared with tradition DSSS system based on a single pseudo-random code, the novel method doubled the transmission rate without decreasing the BER performance or increasing the transmission bandwidth or increasing the signal power per bit.