Starting from the maximum power transfer theorem，we deduce gradually the circuit principle and characteristics of the magnetic resonant coupling wireless energy transmission，then the same conclusion as reported in an article published in Science is obtained. It is shown that the mechanism of the magnetic resonant coupling wireless energy transfer is still in the domain of circuit theory. It also demonstrates that digging in depth and applying creatively the important contents，appeared in basic courses，can play a role in accurately understanding and explaining the new phenomena reported in the scientific foreland.