The invention discloses a distributed detection system for an illegal power utilization behavior of a smart power grid, and a detection method. The distributed detection system comprises a smart electricity meter data acquisition module, a smart electricity meter data transmission module, a smart electricity meter data storage module, a smart electricity meter data security authentication module and a smart electricity meter core computation module. According to the detection system and the detection method, global coverage of the smart power grid is realized; illegal power utilization detection is finished by a smart electricity meter; after system deployment is finished, compared with an original centralized detection system, the coverage range of the system is greatly expanded, emergency situations can be well dealt with, and the precision of computation and detection is relatively high.