Abstract: Flow shop scheduling problems under uncertainty are discussed in this paper.The method of admixture chance constrained programming that includes stochastic parameters and grey(parameters) is researched in order to deal with the uncertainties in the complex systems.The concept and method of grey simulation is proposed through theoretical deduction and verification,which provide a solution method for the grey chance constrained programming.Based on the stochastic simulation and grey simulation,genetic algorithm can be used to get the best results.Finally,the method is used to solve the Flow shop scheduling problem under uncertainty and validated by simulation results.