Abstract: The precise delay computation of combinational circuits is very important for evaluating the performance of the designed circuits and for the optimization of the circuits. This paper analyses the relation between the delay computation of the combinational circuits and its function, and presents an algorithm to compute the precise delay of the circuits. The algorithm eliminates the effects of the false and invisible paths on the delay computation of the circuits. It has been implemented on the computer Sun SPARC Ⅱ.The experiments show that it can get better results than that presented in papers 1 and 3 and can handle the very large scale combinational circuits.