The invention discloses a water-based cold-pigment multifunctional heat-insulating true stone paint for an exterior wall and a preparation method thereof. The water-based cold-pigment multifunctional heat-insulating true stone paint is prepared by mixing water, auxiliary agents, a synthetic resin emulsion, pigments and fillers and natural colorized sand. The preparation method comprises the following steps: firstly, adding water, fiber, a defoaming agent, glycol, a film-forming auxiliary agent and an multifunctional auxiliary agent into a dispersing tank; secondly, adding a styrene-acrylic emulsion; thirdly, sequentially adding a cold pigment, hollow glass microspheres, hollow ceramic microspheres, rutile titanium dioxide, ultrafine talcum powder and infrared ceramic powder; fourthly, slowly adding quartz sand; and finally, adding a sterilizing agent, the defoaming agent and a thickening agent and stirring uniformly. By adding the cold pigment, the hollow glass microspheres and other pigments and fillers, the water-based true stone paint for the exterior wall is endowed with three heat-insulating effects, namely blocking heat insulation, reflective heat insulation and radiative heat insulation; by selecting the water-based synthetic resin emulsion and the water-based paint auxiliary agents, the true stone paint is water-based and environment-friendly; natural quartz sand with different fineness and different colors is used as aggregate, so that the true stone paint has a vivid effect for imitating natural stone, marble and granite, and is rich in paint film color and gorgeous in appearance.