Abstract: In this paper, biochar adsorbent was prepared from waste rice husk by modification with metal magnesium (Mg) and iron (Fe), respectively. The morphology and microstructure of biochars were characterized using scanning electron microscopy and fourier transform infrared spectroscopy. The adsorption performance of the metal-modified biochar on Rhodamine B in aqueous solution was studied. The results showed that the modified rice husk biochar had a rough and porous structure, and the Mg²⁺-modified biochar achieved the removal rate of 94.1% at 480 min under the adsorption conditions of pH=5, pyrolysis temperature of 400 ℃, and adsorbent dosage of 100 mg. The fitting data of adsorption kinetics showed that the adsorption of Rhodamine B by raw biochar and metal-modified biochar fitted the pseudo second-order kinetic model better (R²=0.999), indicating that the adsorption process of Rhodamine B by these biochars belonged to chemical adsorption. The adsorption isotherms of raw biochar and Fe³⁺-modified biochar on Rhodamine B fitted Freundlich model better, while the adsorption isotherms of Rhodamine B on Mg²⁺-modified biochar were more consistent with the Langmuir equation.