Abstract: Frequency synthesizer is the core equipment of modern equipment and communication system. It determines the performance of equipment. At present, the market of RF measurement instruments of China is basically owned by western developed countries. As the price is expensive, the research and development of low-cost frequency synthesizer is very necessary and important. This paper introduced the implementation scheme and key technologies of 10MHz-1GHz small step frequency synthesizer in frequency hopping source. On the premise of certain phase noise and spurs in system, as relative bandwidth for the output spectrum is large, our scheme uses down-conversion method, in which small step is achieved by the DDS + PLL. The whole system is controlled by STC89LE52 MCU, with the advantage of high hopping rate,low cost, small size and so on.