Traditional component design methods pay much attention to component?s usefulness, while usually ignore the optimization on component?s usability, such as reuse cost and reuse efficiency. During the whole lifecycle of component reuse, it is necessary for component to be continuously re-designed so as to reduce reuse cost under the guarantee of high reusability. In this paper, a featurebased component model is firstly introduced, with emphasis on reuse mechanism based on variation point. By analysis of constituents of component reuse cost, the optimization goal, i.e., increasing the proportion of fixed part of a component, is put forward. Then a component optimization method based on variation point decomposition is presented, i.e., decomposing every feature item of a variable feature into a set of sub-items and picking up those common sub-items as much as possible to extend fixed part of the component. Finally the effectiveness of this method is proved theoretically and practically.