The invention discloses heteroatom modified Baijiu vinasse-based activated carbon and a preparation method thereof. The method comprises the following steps: (1) crushing dried Baijiu vinasse, mixingthe Baijiu vinasse with a hard template, adding a heteroatom compound, grinding and uniformly mixing all the components; and (2) in a nitrogen protective gas atmosphere, calcining the mixture in a tubular furnace at 550-950 DEG C for 1-3 hours at a high temperature, cooling the mixture to room temperature, soaking the mixture in 10-40% hydrofluoric acid for 10-24 hours to remove the hard template,filtering and washing the mixture, and drying the mixture at 100 DEG C. The method is simple, convenient, fast and easy to operate, and the prepared modified Baijiu vinasse-based activated carbon isa mesoporous carbon material, has concentrated pore size distribution and large specific surface area, and shows good catalytic activity in catalyzing peroxysulphate oxidation to remove organic pollutants in a water body.