Phase noise is a very important index for radar transmitters and receivers，which can directly indicate the coherence of Doppler radar． In order to understand the physical significance of phase noise, a method for phase noise fault examination is summarized, which can be used to guide weather radar maintenance. The physical significance of phase noise is analyzed, and some disturbance factors from radar transmitters and receivers are studied according to the phase noise calibration principles and test methods. The disturbance factors are carefully discussed and tested to propose a method for phase noise abnormality solution. The phase noise fault examination and analysis for CINRAD/SA weather radar at Heyuan of Guangdong proved that the method is effective.