With the constant improvement of the engine enhanced index, the crankshaft working conditions are even more critical. For designing a better dynamic performances of crankshaft, dynamic optimization design of crankshaft is researched. Boundary restrictions and dynamic loading conditions that simulate the actual ones are exerted on the finite element model of the crankshaft and its dynamic responses are calculated. Based on the sensitivity analysis method, the to-be-modified parameters are selected from the parameters which vary the dynamic properties greatly. With this method, the dynamic properties of the modified crankshaft could satisfy the design requirements, and lays a solid foundation of the dynamic optimization designing of complete engine.