With the features of large electromechanical products like high cost and limit quantity of manufacturing equipment, long processing cycle, uncertain returned repairing work, etc., a resource modeling method based on capability was proposed for supporting manufacturing process optimization. And, mainly from three aspects of resource that were capability, status transition and service cost, manufacturing resource was described in this model. An automotive process and automotive mapping of resource was supported by capability description of this resource. Moreover, how the resource status was changed with the changing of processing task was described in the status transition of resource. Then, when describing service cost, installing and unloading cost was considered as well as expense cost in unit time in order to support the situation analysis of changing tasks in the manufacturing process. So the optimization of manufacturing process of large electromechanical products in a dynamic resource environment was supported by the combination of these three aspects. Finally, combining with a concrete case about manufacturing of rotor which is a key component in steam turbine, the validity of this method was verified.