Abstract: The air-dried rubberwood and the kiln dried rubbervvood were treated respec: tively with 4 kinds of relative humidity: φ = 70, 80, 90, 100%, and with 4 kinds of temperature : t= 15, 20, 25, 30℃. The result showed that the equilibrium moisture content of the kiln-dried rubberwood was 1.91~3.81% lower than that of the air-dried rubberwood, and 2.77~4.11% lower than that from "t-φ-w" diogram. In addition, the swelling coefficient in tangential and radial direction with moisture absorption was 0.18% and 0.11% respectively, 0.06% and 0.05% lower than that of the air-dried rubberwood. No mildew occurred with φ<85%, slight mildew when φ= 85~95%,and heavy mildew when φ>95%. problems concerning mildew resistance and the necessity of kiln-drying for rubberwood were also discussed.