A C-band frequency synthesizer scheme for fullcoherent radar combining direct digital synthesis (DDS) and phaselocked loop (PLL) is proposed in this paper. In order to improve the phase noise and spurious of output signal and reduces the system complexity, the highperformance local oscillator is designed by using HMC704 to control VCO, and the baseband LFM signals produced by AD9910 are further upconverted into Cband by two times to meet the required frequency. The synthesizer has implemented with good performance of both low phase noise, high resolution and small step. Experimental results show that the output amplitude of the proposed Cband synthesizer is greater than 10 dBm, frequency step is 1 kHz, the phase noise level is better than -103 dBc/Hz at 1 kHz,the indicators meet the practical engineering requirements.