Summary: A post-floorplanning wire length optimization algorithm is proposed for slicing floorplan, which considers block swapping, block flipping and white space redistribution simultaneously. For each operator in the slicing tree corresponding to a given floorplan, a binary variable is introduced to decide whether its two children are swapped. Then, we traverse the slicing tree and represent the positions of each block as linear functions of these binary variables. On the basis of this, we formulate the problem as an integer linear programming (ILP) model which takes block flipping and white space redistribution steps into consideration. Experimental results show that our approach can obtain a better wirelength than previous works. Thus, it provides an effective way to further improve the quality of floorplan.