A new method,orthogonal algorithm,is presented to compute the logic probabilities(i.e.signal probabili-ties)accurately.The transfer properties of logic probabilities are studied first,which are useful for the calcula-tion of logic probability of the circuit with random independent inputs.Then the orthogonal algorithm is des-cribed to compute the logic probability of Boolean function realized by a combinational circuit.This algorithmcan make Boolean function“ORTHOGONAL”so that the logic probabilities can be easily calculated bysumming up the logic probabilities of all orthogonal terms of the Boolean function. A new method, orthogonal algorithm, is presented to compute the logic probabilities (iesignal probabili-ties). The transfer properties of logic probabilities are studied first, which are useful for the calcula tion of logic probability of the circuit with random independent inputs.Then the orthogonal algorithm is des-cribed to compute the logic probability of Boolean function realized by a combinational circuit. This algorithm scan make Boolean function “ORTHOGONAL” so that the logic probabilities can be easily calculated bysumming up the logic probabilities of all orthogonal terms of the Boolean function.