The basic concepts and procedures of genetic algorithms (GAs) are briefly introduced here. The main effort of the paper is placed on the literature review of the components improvement basing on the relative papers after 1989. The improvement techniques reviewed in this paper are also concluded in one graph. For the better understanding of GA, one example problem is shown to illustrate the procedures of simple genetic algorithm (SGA). Finally, a short discussion on the advantages and drawbacks of GA is made in the conclusion.