We observed the dramatic enhancement of the intrinsic spontaneous and stimulated emission as well as the ensuing suppression of defect-related green emission in Au-decorated ZnO microrods. A series of spectral experiments and theoretical analysis demonstrated an electron transfer assisted process by surface plasmon (SP) resonant coupling between the Au nanoparticles and ZnO. The mechanism indicates an approach to enhance the UV emission of ZnO through an extra excitation of visible light similar to that for the defect emission of ZnO. Based on the coupling mechanism, the externally enhanced ultraviolet lasing was further improved from 1.5 to 2.8-fold by adjusting the pumping power of the green light intensity in the Au/ZnO hybrid cavity. This research not only further confirms the SPR-assisted electron transfer process but also offers an approach to improve the intrinsic UV emission even for heavily-defected ZnO through visible light excitation via a nonlinear process.