Abstract: With the communication systems of direct sequence spread spectrum(DSSS) as the study object,the anti multipath fading performance of DSSS signals transmitted over multipath Rayleigh fading channel is analyzed under the software environment of MATLAB/Simulink.The DSSS communication system is dynamically modeled and simulated with Simulink.The characteristics of spreading gain,pseudo noise(PN) code length and Doppler frequency shift are analyzed, the relationship curves of the bit error rate(BER) and the signal-to-noise ratio(SNR) of DSSS communication systems are presented,and the influence of multipath Rayleigh fading channel on DSSS signal transmission is introduced.Simulation results indicate that the DSSS system can efficiently overcome multipath fading and Doppler frequency shift in multipath Rayleigh fading channels,although some limitations still exist.In addition,compared with improving the spread spectrum gain,increasing the PN code length is more effective on improving the anti multipath fading performance of the whole communication system.