The invention discloses a silicate cement grinding aid and a preparation method thereof. The silicate cement grinding aid is prepared from the following main raw materials by weight: 3-6 parts of sodium hexametaphosphate, 2-5 parts of aluminum sulfate, 5-8 parts of tetra sodium salt of amino trimethylene phosphonic acid (ATMP.Na4), 4-6 parts of ethylene diamine tetra (methylene phosphonic acid) sodium, 38-45 parts of polymeric alkylol amine, 34-42 parts of triisopropanolamine, 8-12 parts of waste engine oil, 2-5 parts of sodium alpha-olefin sulfonate, 10-16 parts of sorbitol, 15-20 parts of diethylene glycol, 8-13 parts of polypropylene wax, 6-10 parts of oxidized polyethlene wax, 4-8 parts of lignite wax, 20-30 parts of odium thiosulfate, 12-18 parts of sodium thiosulfate and 15-20 parts of quicklime powder. The prepared silicate cement grinding aid has the advantages that the quality is stable, the effect is remarkable, the adding amount is small, the use is simple, and the adding is more convenient and reliable to control.