The invention discloses a chemical mechanical polishing liquid and a preparation method thereof. The chemical mechanical polishing liquid is prepared from, by weight, 15-30 parts of phosphoric acid, 10-20 parts of sodium tetraborate, 10-20 parts of sodium silicate, 10-20 parts of sodium bicarbonate, 10-20 parts of sodium citrate, 25-45 parts of deionized water, 10-15 parts of talcum powder, 8-10 parts of calcium carbonate, 1-10 parts of oxidizing agent, 5-10 parts of liquid paraffin, 2-10 parts of corrosion inhibitor, 1-10 parts of surfactant, 1-9 parts of pH regulator, 1-3 parts of kaolin, 1-2 parts of diatomite, 1-2 parts of lamellar mica powder and 1-2 parts of hollow glass beads. The raw materials are stirred, heated and mixed to obtain the chemical mechanical polishing liquid. The chemical mechanical polishing liquid is effective in polishing, harmless to surfaces of semiconductor chips, safe, nontoxic, free of harmful gases and capable of increasing polishing speed and reducing surface contaminants of polishes materials.