In order to enhance the capability of anti-jamming and Low Probability of Intercept (LPI) of radar system, spread spectrum signals are designed for modern radar system. Emission signal is coded with PN codes at the transmitting terminal. Spectrum of signal is spreaded and multi-signal mixed together, so it is not easy to intercept. At the receiving terminal, undesired signals are spreaded when dispreading desired signal. Signal to noise ratio (SNR) of the received signals is raised after despreading, so the detection range broadens. Computer simulations verify the good performance of the proposed approach.