Abstract: For a better flow monitoring at the borehole of underground gas drainage in coal mines, and in response to the influence of factors such as complex composition, poor purity and poor stability of the medium in the pipeline on the measurement accuracy of drainage flow parameters, a set of adaptive detection system of ultrasonic flow for mining boreholes is designed with the time difference method as the measurement principle and the double threshold comparison method as the detection method. The overall scheme of the detection system is designed based on the analysis of the key problems affecting the measurement accuracy of the double threshold comparison method, and several key modules of the excitation signal amplification circuit, the received signal conditioning circuit and the adaptive circuit composed of the peak detection circuit and gain control circuit are discussed in detail. The workflow of the operation software of the detection system is described. The function and performance of the detection system are tested through the test of adaptability to working conditions and environment and the accuracy performance test. The test results show that the system can adapt to the working conditions in the gas drainage drilling pipeline and realize high-precision gas flow measurement.