In order to meet the requirements of timely and accurate acquisition of downhole temperature, pressure and other data and remote and real-time operation of downhole working system, a new type of long-distance wireless two-way communication detection system is designed in this paper. The system consists of downhole module and ground module. Aimed at the complexity of the fact that downhole communication channel is complex, the uplink and downlink signals need to be transmitted in the same channel and serious signal attenuation and low signal-to-noise ratio, a low-frequency electromagnetic field channel based on time-frequency division multiplexing protocol is designed in this paper, and the weak signal measurement is solved by means of wavelet denoising and other methods. The test results show that the system has successfully realized the bidirectional communication in casing wells for the first time, which is of positive significance to the development of well-testing detection and other technologies that require long-distance detection.