The tunable high performance multi-channel wavelength demultiplexer (WDM) based on metal-insulator-metal (MIM) plasmonic ring resonators is designed and numerically investigated. By the resonant theory of ring cavity, we find that the channel wavelength of WDM can be easily manipulated by adjusting the radius and refractive index of the ring cavity, which is in good agreement with the results obtained by finite element method (FEM) simulations. The multi-channel WDM structure consisting of a plasmonic waveguide and several ring resonators increases the transmission up to 80% at telecommunication regime, which is two times higher than the results reported in a recent literature. The proposed compact multi-channel wavelength demultiplexer can find more applications for the ultra-compact WDM systems in highly integrated telecommunication circuits.