Based on the fact that gate-level power simulation and estimation has high accuracy but low speed, this paper presents a novel method to accelerate gate-level power simulation and estimation. In the gate-level simulation, we only record the switching activities of a small part of cells. For other cells, the switching activities information can be obtained by probability propagation scheme proposed in this paper. This method results in about 20 times improvement of simulation speed with only small error penalty. The proposed method can be used with traditional power simulation and analysis tools easily. So it has been applied in Godson-2 processor’s power estimation successfully