Despite great advances, fire safety is a permanent challenge in expanded polystyrene (EPS) foam specially used as the thermal insulating external wall in buildings and constructions. Herein, an effective flame-retardant architecture consisting of phenolic epoxy resin (PER), ammonium polyphosphate (APP) and tannic acid functionalized graphene (TGE) was successfully fabricated and coated on the surface of EPS foam plate (EPS/ATG) to achieve excellent flame retardancy and thermally insulating properties. This surface coating is equivalent to protective "shield" for expanded polystyrene foam plate. The PER/APP/TGE paintcoat with a ratio of 20:20:0.65 imparted superior fire safety to EPS foam, exhibiting a high limiting oxygen index value of 35.50%, and a UL-94 V-0 classification was achieved with only 300 um of flame-retardant layer thickness. Cone calorimeter test results showed that EPS/ATG20 foam plate was more efficient in decreasing the peak heat release rate by 53.8% and prolonging ignition time by 75.7 times in comparison with the EPS foam plate. Thermal conductivity of the EPS/ATG20 foam plate just increased from 0.048 W/m K of EPS foam plate to 0.053 W/m K. The PER/APP/TGE paintcoat not only endowed excellent flame retardancy to EPS/ATG foam plates, but maintained desirable thermal insulation properties.