Abstract: Floorplanning is one of the most critical stages in VLSI physical design．In this paper，a novel flooplanning algorithm is presented to optimize the floorplan with arbitrarily shaped rectangle blocks and soft blocks．The algorithm is based on the simulated annealing algorithm and the so called sequence pair structure which is presented by Murata and et al．The floorplan quality of this algorithm is demonstrated by several standard example of MCNC．The result shows that the algorithm presented in this paper is very promising．