In the partial discharge monitoring of substation operation and maintenance, the measurement results of ultrasonic sensors are affected by the electric field, magnetic field, environmental humidity, temperature, and vibration, as well as their coupling effects, leading to a decrease in measurement reliability and even signal distortion. Therefore, in order to quantify the influence of multi-physical field coupling of ultrasonic sensors, this paper constructs a sensor test platform with multi-physical field coupling, simulates the complex scene of actual substation, and carries out experimental research on the influence of ultrasonic sensor measurement under single physical field and two, three, four and five physical field coupling. The experimental results show that when only a single physical field is applied, the vibration makes the measured value seriously distorted, and the maximum error is 69%. Without vibration, temperature and humidity have a significant impact on the sensor, and the maximum relative error is 9.4%. Under the coupling of the second, third, fourth and fifth physical fields, the sensor error is as high as 60.3% when the vibration is coupled with other physical fields. Without applying vibration, the change trend of the measured value of the ultrasonic sensor is mainly affected by temperature. Based on the experimental results, a multi physics field coupling influence model of the sensor was obtained, revealing the influence law of multi physics field coupling on the measurement values of ultrasonic sensors, and providing a basis for error calibration of ultrasonic sensors.