The invention provides a highly-phosphorus-doped active carbon material for the negative electrode of a lead carbon battery and a preparation method thereof. The material is composed of the following elements in terms of atomic percent: 1.50 to 5.80% of phosphorus, and 3.50 to 18.40% of oxygen, with the balance being carbon. The preparation method for the material comprises the following steps: 1) treating active carbon in nitric acid with a mass concentration of 10 to 30% at a temperature of 60 to 90 DEG C for 1 to 4 h; 2) adding the active carbon treated by nitric acid in the step 1) into a phosphoric acid solution with a concentration of 0.5 to 3 mol/L and carrying out stirring so as to obtain a slurry-like mixture and drying the slurry-like mixture; and 3) carrying out roasting in a tubular furnace with a temperature of 400 to 600 DEG C for 2 to 5 h in an argon atmosphere and then successively carrying out cooling to room temperature, centrifugation, washing and drying. According to results of the electrochemical performance of an electrode slice prepared from the highly-phosphorus-doped active carbon material, the hydrogen evolution potential of the active carbon material obviously shifts negatively due to phosphorus doping and hydrogen evolution current at a same potential (-1.35 V vs Hg/Hg2SO4) substantially decreases; so a hydrogen evolution reaction on the surface of the active carbon material is inhibited, and the higher the doping amount is, the more obvious hydrogen evolution inhibition effect is.