Abstract: A simple but efficient algorithm addressed for fixed-outline floorplanning is presented in this paper. The proposed algorithm takes sequence pair as representation. It first selects certain modules which have a total width little less than or equal to the width of the given outline, and then transforms these modules into common sub-sequences of sequence pairs. During the process of simulated annealing, the proposed algorithm uses these common sub-sequences to limit the widths of the floorplans while minimizing the areas. Experimental results on MCNC benchmarks show that the proposed algorithm can achieve a highly successful probability, even when tight outlines and large aspect ratios are given. Furthermore, the proposed algorithm takes less time than other fixed-outline floorplanning algorithm, and the feasibility of the given outline will be evaluated at the beginning of floorplanning.