Abstract: In order to evaluate the optimization efficiency of genetic algorithms, this paper presents two indices--"the average truncated generation" and "the distribution entropy of truncated generations". Thereafter, they are unified as a monolithic criterion. Based on this criterion, the optimization efficiencies of several genetic operators are investigated in detail with the example of float-type genetic algorithms. The results show that the variation of genetic operators corresponds to that of optimization efficiencies. The conclusion provides a scientific basis for selecting the efficient genetic operators.