The main signal flow of the frequency source for CINRAD/CC radar produced in the 7th batch is described. Through analyzing the main signal flow of the frequency source and using the waveform of the spectrum analyzer on key points, the fault phenomenon and the solution of the frequency source are discussed. The process is expounded, taking a typical fault phenonmenon for example. Requirements for the CC radar frequency source at the center frequency of key points and spectral amplitude are summed up. Some useful hints are given for radar users and the maintenance staff.