Abstract: In this paper, an efficient and precise calculation method suitable for analyzing dynamic behavior of the structure system of the machine tools is present. In the method, in order to greatly shorten computing bine of the machine design analysis, a component modal synthesis technique (Modal Force Method) is adopted. By studying various complicated joint relations among the components of the machine tools, an analysis mode assembly technique was put forward, which closely integrates component finite element analysis, interface characteristics and modal synthesis. In addition, in order to heighten the accuracy of modal synthesis and meet the need of identifying weak area of the machine structure, some new formulas have been developed. From the result of an example given in this paper, it can be seen clearly that this method has the following advantages:high accuracy, high calculation speed, low requirement for hardware environment etc., and it has given an efficient means for modification of the structure layout and optimum design.