Abstract: On the basis of the principle of energy conservation, this paper reviews the aspects on energy input and dissipation in the coupling processes of the Solar wind, Magnetosphere and Ionosphere (SMI coupling). We focus on the following 9 principle issues: (1) solar wind energy input, (2) magnetosphere response to solar wind energy injection, (3) ring current dissipation, (4) Joule heating in the polar ionosphere, (5) auroral particle precipitation, (6) energy dissipation and storage in the magnetotail, and energy returning from the magnetosphere to solar wind, (7) energy accumulation and dissipation during quiet periods, (8) energy partitioning in different sinks, (9) the criterions and methods for assessing energy function.