sampling oscilloscope is widely used in the field of broadband measurement. As the key device of sampling oscilloscope, sampler converts high-frequency signal into low-frequency signal based on comb wave convolution theory, and the output signal of sampler is transient value, and the symmetry of two output signals is poor. Based on the analysis of the principle of microwave broadband sampler, this paper will analyze the impedance integration circuit of IF signal output by sampler The offset control circuit is designed. Experimental verification shows that based on the designed sampler and impedance integral amplification circuit, 20 GHz RF signal can be converted into 50 kHz IF signal, and the offset control circuit can realize the calibration of signal offset, which can be used in the analog front end of sampling oscilloscope.