The complexity of various complementary settlements for provincial power plants is analyzed.Then a new method of complementary settlement based on the original environment and the separation of complementary settlement from monthly settlement is proposed.A complete set of solution ideas，including analysis of the types of complementary settlement，construction of the original environment，revision of the original environment and complementary settlement based on original environment，is presented to solve the problem of various and repeated complement settlements，while meeting the demand for accurate tracking analysis of the settlement completion progress.The design flow chart of this method and a case study are given.This method is being successfully applied to the provincial electricity market and is capable of satisfying the settlement demand.