The graphene oxide (GO) and modified carbon nanotubes (MCNTs) were dispersed in water and mixed with toluene to form homogeneous emulsion, then the porous graphene–carbon nanotubes composites (MCG) were prepared through hydrothermal reaction. The adsorption mechanism of MCG was investigated by adsorption methylene blue. The morphology of MCG was analyzed by scanning electron microscope and transmission electron microscopy. It was found that MCG had rich micropore structures and MCNTs were interlaced on graphene sheets. The pore size of MCG can be effectively controlled by changing the volume ratio of toluene to the GO/MCNTs solution in the emulsion. MCG was characterized by X-ray diffractometer, Raman spectrometer, X ray photoelectric instrument and other analytical instruments. It was found that MCG had more oxygen functional groups. The experimental results show that kinetics can be well-described by pseudo-second-order model. The smaller the pore size, the higher the equilibrium adsorption capacity and the slower the adsorption rate. The adsorption thermodynamic parameters show that the adsorption process is spontaneous and belongs to physical adsorption, and high temperature is beneficial to adsorption. The fitting results of MCG-5 equilibrium adsorption data are matched with the Langmuir model and the saturated adsorption capacity is 232 mg g−1. After five cycles of adsorption–desorption operation, the adsorption capacity of MCG-5 decreases slightly.