The invention discloses anti-cracking noise-reducing insulating composite cement mortar and a preparation method thereof. The anti-cracking noise-reducing insulating composite cement mortar is prepared from the following materials in parts by weight: 85-100 parts of aerated concrete particles, 20-35 parts of hollow glass micro-beads, 20-30 parts of polyacrylonitrile fiber, 15-30 parts of sulfate, 10-20 parts of calcium oxide, 10-15 parts of basaltic rock powder, 20-35 parts of waste residues, 10-20 parts of methylallyl alcohol polyoxyethylene ether, 10-15 parts of an air entraining agent, 15-20 parts of latex powder, 5-10 parts of an expanding agent and 6-12 parts of a water reducing agent. When the anti-cracking noise-reducing insulating composite cement mortar is used, all the components are added according to proportions, a proper amount of water is added, then uniform stirring is carried out, and construction can be carried out; compared with the prior art, the anti-cracking noise-reducing insulating composite cement mortar has the advantages of easy formation, light weight, good sound-insulating effect, excellent sound insulating and noise-reducing effects and heat-preserving and energy-saving effects, reasonable cost, simple and convenient construction, obvious improvement of the sound-insulating effect and the like; and after the cement mortar is cured, the adhesion among the particles of the cement mortar is better, and the toughness among the particles is strong, so that the cracking phenomenon is difficult to occur.