Abstract: It is of great significance to carry out accurate monitoring of equipment operation status to ensure the safe and reliable operation of distribution network. In order to monitor the operating state of distribution equipment, many sensors are used to acquire the key characteristic quantity. To solve the generality of sensor selection, the author build the improved membership function model on the basic of traditional ridge-shaped function to describe the fuzzy degree between relatively quality grades. It adopts the combination of subjective weight and objective weight for sequence of sensor index. It effectively reduces the error caused by single weighting factor. And it also quantifies membership degree of sensor index and the calculation result is more accuracy.