The combination of ammonium polyphosphate(APP) and silica gel is considered to be efficient flame retardant and smoke-suppresser for wooden materials due to their excellent adsorption and catalysis properties. APP/silica gel could be absorbed by 20.2% in mass in paulowna when using vacuum-pressure impregnation followed with vacuum drying. The wood so prepared were not able to be burned during CONE test, and did not show obvious combustion even burned at 760 ℃. The total heat release for treated paulownia wood was slightly higher than that trea...