Abstract: Loop resistance is one of the important characteristic indicators of substation equipment parameters, which is the key information for abnormal power supply warning and the most reliable indicator of power system performance and attenuation. However, there are many problems with long-distance circuit resistance testing, such as low testing line length, complex measurement operations, and low measurement accuracy. This article proposes a long loop resistance testing method based on wireless transmission to address the above issues. Using the adjacent phase of the tested bus as the current carrying circuit, a 24 bit ADC module, STM32 control module, and LoRa communication circuit were designed. Based on the adjacent phase current carrying circuit resistance test method, measure the voltage of the two phase lines. The feasibility of the scheme was verified through the construction of the system device.