This paper is to discuss the research of heterogeneity in Meta-analysis, including the definition of the heterogeneity in Meta-analysis and classification it into clinical heterogeneity, methodological heterogeneity and statistical heterogeneity, the strategies for diminishing clinical heterogeneity and methodological heterogeneity, the five testing methods in statistical heterogeneity (Q statistic, I2 statistic, H statistic, Galbraith plot and L’Abbe plot) and the examples and applying conditions of the five testing methods, classification of meta-analysis into exploratory meta-analysis and analytic meta-analysis according if the meta-analysis has heterogeneity, and the strategies and the flowchart when existing the heterogeneity in meta-analysis.