In order to meet the measurement demand of the radio, this paper briefly describes the traditional analog frequency-detecting technology, and analyzes the pulse filter method and differential frequency-detecting method in detail. Both of the methods were simulated and compared. Finally the method was given to suit for the portable and low power radio tester. The simulation result proved that this design can avoid the analog circuit’s stability and consistence. When we make use of audio signal processing hardware platform, this design can improve the integration of the system design also.