A novel biomass carbon doped with dual-metal oxide mischcrystal (cobalt oxide and molybdenum oxide) was synthesized by using Enteromorpha (EP) of marine algae as carbon source. Multi-wrinkles biomass carbon (MWBC) with magnetic properties was obtained and formed highly dispersed CoOx/MoOy nanoparticles onto the surface of MWBC in situ via a simple impregnation and direct carbonization at 700 degrees C. The framework of CoOx/MoOy@MWBC was characterized by scanning electron microscopy, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The as-prepared CoOx/MoOy@MWBC was applied as efficient adsorbents for selective removal methyl blue (MB) at pH 10 from water medium. For comparison, single metal-derived porous carbon, i.e., CoOx@MWBC and MoOy@MWBC, was also synthesized, characterized and tested for MB adsorption. The results exhibited that CoOx/MoOy@MWBC has the highest MB adsorption capacity (1587.3mgg(-1)) and excellent selectivity. In addition, it could be easily separated from water by an external magnetic field without any organic reagent added. Adsorption equilibrium data were described by Langmuir and Freundlich isotherms, and kinetic data were described by pseudo-first-order, pseudo-second-order and intraparticle diffusion model. Moreover, CoOx/MoOy@MWBC also owned outstanding stability and renewability, which can be regenerated by an easy-going method of ethanol washing and reused at least 10 times without a significant loss in removal percentage.