The removal mechanism of U(VI) from water by biochar loaded nano chlorapatite, denoted as BC/nClAP, and the effect of humic acid on the removal process were experimentally investigated. The materials were also characterized by XRD, SEM, FTIR and XPS. The results showed that the biochar-loaded nano chlorapatite had a good removal effect on uranium in water (when the initial concentration of U(VI) was 5 mg/L, the dosage of BC/nClAP was 0.1 g/L, and the pH value was 4.0, the removal rate of U(VI) by BC/nClAP was as high as 99.7%), and the humic acid had a significant effect on the removal effect and shortened the equilibrium time of the adsorption (shortened the equilibration time from 30 min to less than 5 min). Regardless of the presence or absence of humic acid, the removal of U(VI) by BC/nClAP could be fitted by quasi-secondary kinetic equation and Langmuir isothermal adsorption model. It was shown that the process of U(VI) removal by BC/nClAP was monomolecular layer chemisorption. The removal mechanism mainly includes dissolution-precipitation and complexation of oxygen-containing functional groups on the surface of biochar. Humic acid affects the adsorption process probably because humic acid seizes the adsorption sites; and it forms a free-in-water U-HA complex with U(VI), which alters the surface interaction of U(VI) and HA with the material.