Abstract: This paper deals with the water absorption of planted Chinese fir treated by hot air and hot vegetable oil respectively for different processing times and temperatures were reported, the water repellence efficiencies(RWE)、anti-shrink efficiencies(ASE) and surface contact angles of samples which were treated by heating treatment were determined, and changing rules of main components of heat treated samples were investigated by using chemical analyzing method. The results showed that heat-treatment evidently decreased the water absorption of treated samples compared to the reference samples, the higher the temperature and longer the heat-treating times, the higher the RWE and ASE, in addition, the effect of heat medium on the dimensional stability of samples were obvious, the dimensional stability of the samples when the treatment in hot oil appeared to be slightly higher than that of samples when the treatment in hot air under the same conditions for processing temperatures and times. The chemical analysis of wood component indicated the mechanisms of heat treatment on improving dimensional stability of wood mainly be attributed to chemical changes of wood cell wall components such as the degradation of the most hemicelluloses and less cellulose during heat treatment.