In order to accurately measure the parameters of the signal, a wideband AC and DC signal detection system is proposed, the STC12C5A32S2 microcontroller is used as control chip of the system. First, the signal is collected by the AC and DC and signal measurement circuit is processed and analyzed. Then, the signal will be processed by dividing and automatic gain amplification circuit, the frequency and phase of the signal is measured in the frequency and phase detection circuit. Finally, the amplitude, phase and frequency information of the signal is shown on the LCD. In the experiment, the signal with 0-20KHz frequency at different amplitudes is measured, the experimental results shows that the measurement error can be ignored in the low-frequency signal measurement, and in the high-frequency signal measurement error is less than 1%.