Abstract: Biochar is a product of pyrolysis of biomass under anoxic conditions; however, common biochar has a small surface area, underdeveloped pore structure, few surface active groups, and poor adsorption effect. In this work, biochar was prepared from sorghum (GC) and grapefruit peel (YC) by surface treatment using four substances to obtain biochar, where the prepared sorghum/KOH (GC-KH) and grapefruit peel/KOH (YC-K) powders had obvious surface porosity, confirming the feasibility of the process. With a specific surface area of 2096.05 m²/g and an average pore size of 4.12 nm, GC-KH is rich in oxygen-containing functional groups on its surface, providing a good structural space and active sites for adsorption.The effect of different factors on phosphate adsorption was explored by batch experiments to assess the ionic strength. Results of isotherms showed that the adsorption of phosphate by GC-KH occurred on the surface of the monomolecular layer, and the maximum adsorption capacity of phosphate by GC-KH was 74.73 mg/g at pH=7. It has significant advantages such as rapid response, which provides an innovative pathway for the efficient removal of phosphate from wastewater.