In order toimprove the quality of the original research evidence retrieval， present study proposed the concepts of saturation and redundancy based on the traditional retrieval assessment index such as recall and precision ratio for the purpose of construct a theoretical foundation for retrieval efficiency from the evidence-based research perspective. Taking the original documents of specific research topics in the field of Social Sciences in CNKI database as samples， this paper systematically searches， analyzes and grades the original document evidence by using a variety of retrieval methods， reference iteration and representative author retrieval for example， which is expected to provide a data basis for the quality evaluation of documentary retrieval in the further research procedure.