Water-based acrylic dispersion is used as binder for low volatile organic compounds (VOCs) in flame-retardant coatings. By combining three halogen-free additives: an acid source (such as ammonium polyphosphate, APP), a blowing agent (such as melamine, MEL) and a carbon source (such as pentaerythritol, PER) with the additives as: dispersing, coalescent, defoams, the authors have made successfully an environmentally friendly flame-retardant coating for applying on ordinary combustible materials such as plastic, wood, foam insulation board. After applying the flame-retardant coating, the results showed that the fire protection for combustible materials were significantly increased, and achieved the requirements of V-0 level according to UL94:2010. The test of the fire protection on foam insulation board conducted under ISO 9772:2012 achieved the requirements of HBF level.