Abstract: Aiming at the fuzzy and correlation among technical evaluation indexes in the mechanical system design scheme, the paper studied the decision-making problem of mechanical system design scheme. Based on the preferred subjection degree and grey incidence, the method of improving grey incidence fuzzy decision-making was proposed. It aimed to seek the optimal design scheme of complex systems from the whole perspectives. Original datas were non-dimensionalized and normalized by using fuzzy math subjection function theory. The technical index weight set and grey incidence coefficient matrix were built to avoid the information loss of technical indexes in the evaluation process. The fuzzy optimization of mechanical products overall design scheme was implemented through a comprehensive evaluation model. Finally, YF27-315 type thin plate hydraulic press punching was taken as an example. The verified model can effectively reduce subjective disturbance in the evaluation process and make the decision of mechanical products design scheme more comprehensive and objective.