This study utilized glucose as the main raw material to prepare carbon nanospheres (CNs) using a hydrothermal method. Polyvinylpyrrolidone (PVP) was employed to modify the CNs, resulting in PVP grafted CNs (PVP-g-CNs). The structural morphology and functional group changes of the CNs before and after modification were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Additionally, the dispersibility and adsorption performance of the modified CNs for methylene blue (MB) were tested. The results showed that the modified CNs exhibited an increased size and altered surface structure, while the amorphous crystal structure remained unchanged. PVP-g-CNs demonstrated good dispersibility in water, and adsorption tests revealed that when the PVP addition amount was 0.50 g and the MB solution mass concentration was 30 mg/L, the maximum adsorption capacity of PVP-g-CNs for MB reached 155.03 mg/g, with the adsorption capacity increasing with the pH of the solution. The fitting results of the adsorption model showed conformity to the pseudo-second-order kinetic model and the Langmuir model, with a theoretical maximum adsorption capacity of 238.095 2 mg/g, thus demonstrating excellent adsorption performance.