Through the analysis of the symmetry fuzzy optimization in the structural design, on the basis of the construction of the iterative criterion, provides the fuzzy method of the objective function and constraints, and give the building method of the fuzzy optimization model and solving flow chart. Takes the spindle device of a marine engineering equipment for the sample, according to its design requirements and characteristics, build the spindle device fuzzy optimization design model, make it the smallest mass in ensuring the strength, stiffness and other conditions. The solved results showed that fuzzy optimization design method is to solve the structural optimization with good development potential, laid the foundation for large-scale equipment complete machine optimization and simulation.