Signal probability calculation is the key to power estimation when optimizing power of MPRM (Mixed Polarity Reed-Muller) circuits by using signal probability based power estimation models. A probability expression based power estimation method is proposed for MPRM circuits. The proposed method takes into account both efficiency and accuracy of signal probability calculation

for signals having not spatial correlation in MPRM circuit

their signal probabilities are computed by means of signal probability propagation in circuit

whereas for signals having spatial correlation

probability expressions are utilized to calculate their signal probabilities and are propagated in circuit to resolve spatial correlation problem

then the dynamic and static power of the circuit are computed respectively by using the established analytical power estimation models based on signal probability. In order to further improve time efficiency

the proposed method utilizes binary moment diagram to represent probability expression. The proposed method is validated by using several benchmark circuits

and compared to other power estimation methods using different signal probability calculation methods for MPRM circuits. Results show that the proposed method is accurate and effective.