Considering many lighting energy-saving modification programs have the phenomenon of diseconomy; this paper takes into account economic evaluation to solve this problem. The optimal program of total energy-saving benefit will be found under the limited investment according to economic evaluation of the price, life span and power consumption of lighting equipments. Firstly, the benefit ratio will be used to evaluate on the necessity of modification, and get the order. If the biggest benefit ratio exists in different equipments simultaneously, the better one will be selected in terms of relative payback period of investment. And on the basis, the relative remaining time is innovatively introduced into economic evaluation to determine the locations of modification. Then an example from a factory can prove that the program is workable.