The invention provides low-temperature quick-drying primer-topcoat water based paint and a preparation method thereof. The water based paint is prepared from an A component and a B component in mass ratio of (0.7-0.9):1, wherein the component consists of 10-15 parts of organobentonite, 20-30 parts of wollastonite, 3-15 parts of nano-titanium white and 1-10 parts of a dispersing agent according to parts by mass; the B component consists of 5-20 parts of an anion single-component epoxy emulsion, 1-5 parts of organic amine and 5-15 parts of a pure acrylic emulsion; the anion single-component epoxy emulsion contains linoleic acid and single-component epoxy resin, and the mole ratio of the linoleic acid to the single-component epoxy resin is (0.7-1):1. The low-temperature quick-drying primer-topcoat water based paint provided by the invention has good constructability in winter and is quickly dried in construction in winter without cracking.