Abstract:Twenty four species growing in Hainan Island were sampled to study the equilibrium moisture content of wood(We) in Haikou region. the experiment lasted 26 months and got the values of We of the species from 14.6% to 1 9.3 %, averaging 17. 1 %,and the difference, 0-2 %, between months within a year. The differences among species and between sapwood and heartwood of Artocarpus styracifolia were highly significant. The regression equation, We =5. 0904 + 0. 1683φ - 0. 0777t, obtained can express the relationship between We and relative humidity(φ) and temperature(t) in Haikou region. Based on the equation a t-φ-We figure was drawn.