This thesis focuses on the influence of VCO modulation voltage on LFMCW radar beat signal. Firstly, analysised the serious effect to beat signal spectrum caused by flyback voltage. Because of the false frequency component would be produced by voltage flyback. So that the radar measurement system can't be measured the correct distance information from the inaccurate peak detection. Thus, both digital signal processing and hardware produce synchronized signal are used to solve the bad influence by voltage flyback brought to LFMCW radar. Finally, compared the processing results with the null group, results shown that modulation voltage flyback would brought great difficulties on signal spectrum analysis, thus, the disturbance signal of flyback section should be processed during practice.