The invention discloses a one-step method for in-situ preparation of carbon coated manganese carbonate for the negative electrode of a lithium ion battery .The method specifically comprises the steps of 1, preparing potassium permanganate solution of certain concentration and carbon source solution of certain concentration respectively, wherein the molar concentration ratio of the carbon source solution to the potassium permanganate solution is 1:(2-2.5); 2, adding the carbon source solution to the potassium permanganate solution, and conducting stirring dispersion and ultrasonic treatment in sequence; 3, adding dispersed solution into a reaction still to be heated for 3-24 h at the temperature of 120-180 DEG C; 4, naturally cooling the reaction still to room temperature, and conducting cleaning and drying to obtain powder, namely the in-situ carbon coated manganese carbonate for the negative electrode of a lithium ion battery .Raw materials for preparation are cheap and easy to obtain, operation is easy, energy consumption is low, pollution is avoided, carbon coating of the obtained manganese carbonate is uniform, size distribution is uniform, purity is high, particle collapse during charging and discharging of manganese carbonate can be effectively prevented, and the cycling stability of the lithium ion battery is improved.