The dynamic characteristics of joint interfaces affect the dynamic behaviors of a whole machine tool structure notably. This paper proposes a dynamical active design method for fixed joint contact area topology of the machine tools. First, the contact stiffness model of the fixed joint with actual contact region is equivalent to a finite element model, the calculation method for material model: elastic modulus and shear modulus is presented, and the contact element stiffness matrix based on the constitutive model for fixed joint is established. Then, Evolutionary Structural Optimization method is used to carry out the optimization design for the fixed joint contact area topology. That is, the delete rule is used to eliminate the contact area which has little contribution for overall natural frequency. Finally, through the engineering case of the fixed joint for bed and head, realizing the active design of the actual contact area topology for fixed joint, and this method is proved feasible and practical. Key words: Fixed joint Contact Topology Design method Machine tool