Abstract: To get A_i of the synthesized system consisting of no less than two units, a new method of bisection is presented on the basis of solving differential state equations. Given the same parameters, all instant state A（t） in different available periods nearly equals to each other, as well as the steady state A, the difference is on 10^-3 quantity stage. In the same conditions, the difference between results from the original model and the steady state A is too significant to be ingored. It is more than 10^-2, especially in short operational cycles. The work provides a reliable warrant for computing A_i of systems and estimating it by a given threshold.