Abstract: For the purpose of reducing the number of the critical paths in timing-driven placement, a powerful new technique to optimize timing via preassigning cell based on linear programming (LP) is represented.The new locations of the cells on the timing critical sub-circuits are optimized by LP and the cells are preassigned to the new locations before the next placement iteration.This method is embedded into the global force directed placement process of Kraftwerk, and the experimental results show that the average worst slack improves 21ps and average total negative slack reduces 483ps while the average wire length only increases 0.83%.