This paper analyzes the effects of metamaterial slabs with negative permeability when applied to a two-loop wireless power transmission (WPT) system, both in theory and electromagnetic (EM) simulations. The analysis of magnetic flux focusing provided here assumes quasi-magnetostatics or magnetostatics. The slab structures with negative permeability have been realized using the periodically arrayed ring resonators (RRs) at 13.36MHz. Some examples with ideal lossless slabs of -1, -2, and -3 showed a great enhancement of WPT efficiencies when compared with the free space cases. However, practical lossy slabs made of planar copper RRs did not show significant enhancement of WPT efficiencies due to the relatively high losses in the ring resonator (or in the slab consisting of RRs) near the resonant frequency.