Compared with classic systematic review types, the scoping review, mapping review and evidence gap maps (EGMs) address broader research questions. Therefore, they are classified into the "big picture review" family. These three types of evidence synthesis have developed rapidly in recent years, but the related concepts are easy to be confused. This article introduces the methodological development process of the three types of evidence synthesis, summarizes the similarities and differences in terms of research purposes and methodology based on the methodological guidelines of the three types of evidence synthesis in the "big picture review" family. The author hopes that this article can help domestic researchers distinguish and identify the three types of evidence synthesis, avoid conceptual confusion, and correctly choose the type of evidence synthesis in the "big picture review" family according to the research purpose.