The invention relates to dividing seam energy-saving paint and a preparation method thereof and belongs to the field of building materials. The dividing seam energy-saving paint comprises resin, fillers and adjuvants. The fillers comprise Danqiangsi, calcium sulfate whisker, zeolite powder and slag powder. The adjuvants include ammonium polyphosphate, an organophosphine/bromine complex, sodium tripolyphosphate, water glass, acrylamide, attapulgite, a binder, a coupling agent and a defoamer. The dividing seam energy-saving paint has excellent cracking prevention performances, a low thermal conductivity coefficient and good thermal insulation effects. The preparation method comprises mixing the raw materials of the fillers according to a ratio to obtain the fillers, mixing and curing the resin and the organophosphine/bromine complex to obtain cured resin, then mixing the cured resin and the remaining adjuvants to obtain a mixture and mixing the fillers and the mixture. The preparation method is simple, is easy to control, has short time consumption and is suitable for industrial production.