Abstract: A simplified thermal model is presented based on an accurate model. The approach is fast than the original one. It was applied to calculate the temperature of each heat source and its contributions to other sources. The superposition principle is applied. The optimization objective is to minimize chip's area as well as to make the thermal distribution as evenly as possible. The simulated annealing was employed in our algorithm. The experimental results show that the thermal distributed evenly and the temperature of the “hot spots” decreased greatly in the chip.