An optimized maintenance scheduling model is presented with economic performances as objective function. The power outage losses include two parts， i.e.， apparent losses and hidden losses. The variations of reliability value index and risk index are used to measure the hidden losses. The line overloading， node over-voltage and frequency stability are used to describe the risk index variations， and the variation of expected energy not supplied（EENS） to the reliability value index variation. The hidden losses model is applied to the maintenance scheduling optimization. By using Benders method， it is decomposed into two problems， i.e.， multi-objective hybrid integer programming and associated random fuzzy problem. The model is used to optimize daily， weekly and monthly maintenance scheduling in the Yunnan electrical transmission system. Compared with the particle swarm optimization（PSO） algorithm and genetic algorithm（GA）， it demonstrates a lot of advantages.