Abstract: A new dynamic characteristic modification method is proposed for structural optimum design and modification. Based on the dynamic characteristic of an original model, the transform analysis of undamped system equation is performed with the frequency characteristic functions at designated modification freedoms, and the general expressions of local mass and stiffness parameters are derived. Numerical examples and a three-story masonry of half scale model test are given to demonstrate the validation of the modification method and the general expressions, and the modified results can meet the predetermined requirements.