Abstract: According to the cell libraries based mapping,the circuits in the libraries were pre-designed and could not be changed during the mapping process which influenced the optimization of circuit area.Thus a Library-free mapping technique,in which the cell circuits were generated dynamically under the corresponding constraints,was introduced in this paper for area optimization.The proposed method mainly consisted of two components: 1) the estimation of the dynamic cell circuit area using both logic effort and the logic function expression; 2) a covering algorithm for the circuit area optimization based on the area estimation.The proposed method is tested under MCNC benchmarks.The experimental results show that compared to ABC tool,a further area optimization can be obtained by the proposed algorithm.