Abstract: A combination decision model of scheduling rules based on simulation is presented for multi-objective problems of job shop scheduling.The scheme group is first obtained using simulation for different combination of scheduling rules.The weight of performance target for manufacturing system is derived with the application of analytic hierarchy process(AHP).The conjunction coefficient of every scheme within the group for the single performance index is then computed.Scheme evaluation based on grey relational analysis is ordered and the corresponding optimizing scheduling rule is derived.Combination decision of scheduling rules based on simulation embodies the performance weight requirement of user for the manufacturing system,and provides the optimizing scheduling rule to resolve the traditional application problem.