Abstract: As an eco-friendly and low-carbon material, biochar is characterized by good stability, low cost, large specific surface area and rich pore structure. However, with the in-depth study of the adsorption behavior of biochar, it is found that its adsorption capacity for anion and heavy metal pollutants is limited, and there are difficulties in solid-liquid separation. In addition, the adsorption performance of biochar is limited by the type of functional groups, the number of adsorption sites and long-term stability, which affects its application in environmental treatment. In order to improve the adsorption performance of biochar, metal-modified biochar has emerged. Metal-modified biochar is a new type of adsorbent material that loads metal elements on the surface and pore channels of biochar, and closely combines the good porous structure of biochar with the catalytic, magnetic, and electrochemical properties of metals, which has a great potential for application in environmental protection. This paper describes the principle, adsorption mechanism and the selection of metal elements of metal-modified biochar; reviews the preparation techniques of metal-modified biochar, including impregnation, precipitation, chemical vapor deposition and sol-gel method, and explores the application effects of metal-modified biochar in the adsorption of hazardous gases, treatment of wastewater and remediation of soils, which confirms the high efficiency of metal-modified biochar. On this basis, it is pointed out that the optimization of the modification process and the development of multi-solid waste synergistic metal-modified biochar is an important development direction in the future.