Abstract: A stochastic scheduling model for hydrothermal power systems is presented based on fuzzy chance constrained programming,taking reservoir inflow and water level for a random variable.Reservoir water volume at the initial hour was formulated as a triangular fuzzy number,representing forecasting errors of reservoir water level.Aiming to represent stochastic variable characteristics due to historical data errors,fuzzy stochastic variables were used to represent the uncertainties incurred in optimization scheduling of hydrothermal power systems.A control function was introduced to coordinate the three objective functions,which includes coal consumption minimization,reservoir water level maximization and air pollutant emission minimization.A stochastic scheduling model of hydrothermal power systems can be converted into a determined form using fuzzy chance constrained programming and random chance constrained programming.A system with 8 cascaded plants and 6 coal-fired plants was taken as a study example and the results show that the model is correct.