Abstract: Traditional approaches to reducing thickness swelling rely on high resin and wax addition which increases manufacturing costs,or heat/steam/chemical treatment which often reduces product strength properties simultaneously.Being inquired into the root of thickness swelling,the structure and characteristics of wood and the interactive relationships of temperature,moisture,pressure and time during hotpressing may play an important role.In this paper,the swelling behaviors of flakes in the different layer of mat under the interactions of heat,moisture and pressure and the swelling profile of commercial flakeboard were investigated.The results indicated that the pressing temperature affected thickness swelling of flakes significantly.A strong correlation was exhibited between the thickness swelling and compression ratio under low pressing temperature.However,under high temperatures,the thickness swelling of flakes from the surface layer was lower than that of the core layer though imposed high compression.To reduce thickness swelling of OSB or flakeboard,the higher pressing temperature is recommended.