This paper proposes a novel load profiling method with the combination of firefly algorithm (FA-LP) for detecting abnormalities of electricity customer. First, a novel approach to model profile method is proposed using the load data from the similar customer in the same region. Second, the load pattern is extracted with the firefly algorithm. Third, the load data are processed differently and two matching measures are adopted according to the different focuses on the load pattern. Finally, the proposed load profiling method is applied for the real case of a power supply company.