Credit rationing problem in agriculture can seriously restrict the process of agricultural modernization. The paper starts from the definition and types of credit rationing, systematizes the classic literature and the latest research progress on credit rationing, summarizes and expands the types of credit rationing, introduces the concept of discriminatory rationing, and reclassifies the concept of volume rationing. In addition, the paper summarizes the research results on credit rationing in the agricultural sector from two perspectives: ″internal″ and ″external″, and believes that future research should be further studied from the perspectives of theoretical depth and differentiation of national conditions.