Abstract: Rain and flood are valuable natural resources. Utilization of both rain and flood resources has a long history and is one of vital water resources utilization ways. In recent years, practical technologies of rain and flood resources utilization have advanced greatly, but there are still remarkable misunderstandings on their basic conceptions. Extensive use of some nonstandard terms has brought confusion to scientific research and practice. Therefore, in light of the relevant history and reality, and according to the basic theory of hydrology, a discussion on rain and flood resources utilization was carried out and preunderstanding was obtained in this research. The natural resources and water resources properties of rain and flood were clarified. Then, the basic connotation and definition of rain and flood resources utilization were summarized. And finally the relationship between rain resources utilization and flood resources utilization was analyzed. In addition, the normalization of some technical terms including so called rainwater reuse and flood reuse was clarified. This paper is helpful to eliminate the misunderstandings about rain and flood resources utilization and consolidate the theoretical basis of the safe and efficient utilization of rain and flood resources. Our understanding creates good prerequirements for the scientific evaluation, planning and technology innovation of rain and flood resources utilization.