The invention relates to an oscilloscope with an improved front-end circuit, the oscilloscope includes a front-end circuit and a control processing module, the front-end circuit includes an input stage buffer and addition circuit, a gain selectable amplification module, an A / D conversion circuit and a D / A conversion circuit , the input stage buffering and adding circuit sequentially passes through the gain optional amplification module and the A / D conversion circuit to the control processing module, the gain selection output end of the control processing module is connected to an input end of the gain optional amplification module , the other output terminal of the control processing module provides a front-end circuit bias signal through the D / A conversion module, and the bias signal is output to the input stage buffer and adding circuit. The oscilloscope of the present invention improves the minimum resolution of ADC input, reduces the demand for analog front-end gain, and uses the switching of amplifiers with several gains at the same time, combined with digital gain, which not only saves costs, but also improves the input ADC signal. signal-to-noise ratio.