A water-based fire resistive nano-coating was prepared via adding CaAlCO3-layered double hydroxides (CaAlCO3-LDHs) as an inorganic filler to intumescent fire retardant coating. The influence of CaAlCO3-LDHs on the coatings properties was investigated by thermogravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cone calorimeter (CONE) and fire performance test. The results showed that CaAlCO3-LDHs could improve the quality of the residual char layer, increase the degree of the cross-linking and the carbon accumulation, and enhance the oxidation resistance of the char layer. The addition of 5 mass% CaAlCO3-LDHs to the coating could reduce the fire hazards of the coating itself, lower the rate of flame propagation and thermal degradation, and improve the char structure and fire resistance of the coating, which was attributed to the synergistic effect of CaAlCO3-LDHs and the intumescent fire retardant (APP/PER/MEL).