The invention discloses water-proof thermal-insulation heat-preservation mortar and a preparation method thereof. The water-proof thermal-insulation heat-preservation mortar is prepared from the following components in parts by weight: 30-50 parts of cement, 20-30 parts of heat-preservation filler, 20-30 parts of ash calcium powder, 10-30 parts of hydrated lime, 10-20 parts of activated kaolin, 5-15 parts of nano-silica powder, 15-25 parts of polymer emulsion, 5-10 parts of gelatin, 2-8 parts of modified straw powder, 5-15 parts of quartz powder, 3-8 parts of redispersible latex powder, 5-15 parts of alumina hollow micro-spheres, 4-10 parts of hydroxypropyl methyl cellulose, 3-10 parts of reinforced fibers, 2-6 parts of an organosilicon waterproofing agent, 1-5 parts of a water reducer, 3-8 parts of a water-retaining agent and 60-80 parts of water. The water-proof thermal-insulation heat-preservation mortar has the characteristics of high waterproofing, efficient heat preservation, efficient thermal insulation, environmental friendliness and the like and can be widely used for projects of heat preservation, thermal insulation, waterproofing and the like of internal and external walls of buildings.