Great attention has been paid to the issue of natural resources all along. After further analysing the nature and definition of natural resources,the author deduces that whether the sustained use of natural resources can be made or not is the key to avoiding the scarcity of them and sums up four major reasons which cause the scarcity of natural resources in this paper. namely, physical limits, geo-political aspects, economics and environment. At last. in view of the interaction between human activities and geographical environment,the author point out that resource science is a disciplinary system which takes the system of natural resources as its object of study.