Fuzzy C-means Clustering is the general load classification algorithm, However, the FCM is sensitive to the initial clustering center and cannot automatically determine the clustering number. In order to solve the problem, this paper proposes a modified FCM clustering method. The modified FCM clustering method utilizes an fast algorithm to determine the clustering center curve and clustering number firstly, the computer result is treated as the initial input of FCM, then use FCM to classify the power load. The modified FCM clustering method can reduce largely manual handling works. The practical examples verify the correctness of the proposed clustering method.