Integration of semiconductors and magnetic materials has attracted a lot of research attention because such integration serves as a promising platform that introduces magnetic functionality into a semiconductor, enhancing the performance and expanding its applicability. For magneto-optoelectronic applications, the basic principle is to achieve the magnetic-field-controlled absorption properties of photon-sensitive materials. This effect is called magnetoabsorption (MA). It is expected that the modification of MA can change the photon absorption by the materials under an applied magnetic field. This is accompanied by a change in the delocalization of electrons by applied magnetic field; this electrons flow induces an electric current that can be utilized in magneto-optoelectronic devices. Although applications have already begun to be developed, gaps still exist in our understanding of the MA effect. In this paper, we describe a series of MA experiments on Co-coated ZnO NWs with Au decoration. Au decoration around the core of the Co/ZnO NWs can induce a sequence of alternating negative MA and positive MA effects due to the modification of the charge transfer in the spin-polarized band of Co/ZnO NWs with Au decoration via magnetoabsorption effect. Although we concentrated on the mechanism governing the MA effect, the large positive MA effect, particularly in the relatively low magnetic field region at RT, resulting from suitable Au coating is an interesting observation, which should be investigated in future studies. Their use in optoelectronic devices is promising for novel magnetic-field-controlled photo-devices and photo-catalytic applications with a magnetic-field-enhancement effect. We believe the results presented herein provide new application domains of spin related optoelectronics.