On the basis of the latest theories about the core training, combined the shortcoming in the understanding of core strength, the author reviewed the concepts of core strength and tried to make some ideas clear. Core strength has two parts: core satiability strength and core mobility strength. The three systems, besides controlling subsystem, initiative system, passive system, there have the forth system: breathe system. Core strength training includes static training and dynamic training, and the two methods must be combined together in sport training.