The radar waveform design for weak target detection in interference and channel noise is considered. Based on the principle of maximizing the SINR, combined with the advantages of the phase-modulate method and the Optimum Transmit-receive Design method (OTRD), a synthesized waveform design method based on phase modulate and OTRD is put forward. Through the simulation, a larger SINR is obtained compared to the previous two methods, the effect is particularly obvious for weak target detection in strong interference, consequently, the function of radar detection is promoted obviously.