The compatibility of the stepped frequency mode and pulse Doppler mode has been studied based on the conical scanning system.The signal selection between stepped frequency and pulse Doppler was analyzed in theory.The arithmetic and the application of the conversion between the two systems were discussed.Outside test was validated about high rang resolution and angle measure of MMW seeker under the compo site system of stepped frequency and pulse Doppler.The result shows that the high rang resolution and angle detect for rest and move target is feasible based on the compo site system of stepped frequency and pulse Doppler.