The invention discloses a method for manufacturing chromatographic silica gel, which comprises: adding water (0.6 MPa) in solid sodium silicate to prepare a sodium silicate solution; adding a template agent after adding sulfuric acid, and reacting to generate a plurality of gel particles; and obtaining the chromatographic silica gel product after technological treatments of aging, acid base modification, water washing and drying, wherein the average pore diameter of the chromatographic silica gel product is between 2 and 20 nanometers, the iron content (as calculated by Fe2O3) is less than 80 ppm, and the content of heavy metals is less than 30 ppm. Due to addition of a template agent A such as organic acid, alkylphenol polyoxyethylene, fatty alcohol polyoxyethylene or polyoxyalkylene block polyether into a sulfuric acid solution, SiO2 molecules are more firmly condensed, and the adsorption capacity of the chromatographic silica gel is doubled. A template agent B, namely alkyl trimethyl ammonium halide, is added into the sodium silicate solution, and the pore diameter of the chromatographic silica gel reaches 2 to 20 nanometers through pore expansion function of alkane ammonium ion groups in gel reaction.