The invention provides a heat insulating and preserving coating for an exterior wall of a building. The heat insulating and preserving coating comprises the components: polymer emulsion, functional filler, titanium dioxide, a thickening agent, a wetting agent, a dispersing agent, a defoaming agent and water, wherein the functional filler is a self-prepared fly ash zeolite molecular sieve; the polymer emulsion is soft styrene-acrylic emulsion. The coating has the advantages that a coating layer formed on a building wall body is outstanding in performance, the heat insulating and preserving effect is superior to that of other similar heat preserving coatings, and the temperature difference can reach more than 10 DEG C compared with a blank phase; in addition, the heat insulating and preserving coating has the advantages of being environmentally-friendly, nontoxic, high in adhesive force, difficult to crack, easy to construct, etc., is applicable to the coating layer for heat preserving of the exterior wall of the building, and shows a remarkable environmental protection and energy saving effect.