Meta-analysis enables researchers to analyze the findings of studies related to the specific area in the form of a specific research question. Based on the results of these reviews for the specific subject, the foundation of new theories and models was established. Often, with investigating studies related to a particular field, we will saw that there are as many studies which were conducted on the same variables. Although similarity in the subject under investigation, it is possible that the methodology, for example experimental vs. survey, or populations of these studies were different. Since, the result of these studies often is not similar, thus there is a need for method to could improve our knowledge about the research subjects, on the base of synthesizing the results. By the same token, regarding to the aim of combining the findings of previous statistical research, meta-analysis follows two major processes: 1- in addition of summarizing, and description the results of studies in the literature of specific subject, it will yield us degree of true relation or difference in the population of various studies; & 2- the estimation of affect of methodological properties on effect size of estimated difference or relation in different studies in the specific field. In the present paper, approaches, goals, advantages, disadvantages of meta-analysis procedure in the field of social, and behavioral sciences were discussed.