<p>In this paper, an extension of the description model in the moving morphable components (MMC) method is made to improve efficiency of computation. We observed that as the optimization via the MMC method progresses, some components may be hidden or become very small, thus having trivial contribution to the performance of structure. Inspired by such a fact, we assign a topology variable to each component to indicate and control its existence. When a component’s topology variable is close to zero, it is ignored in the subsequent computations, including computing topology description function, sensitivity analysis, and seeking the optimal value of design variables, hence saving much computation time. In addition, a constraint of topology variables is introduced into the optimization to drive them converge to either 0 or 1. Numerical examples demonstrate the effectiveness and efficiency of the proposed approach.</p>