An air-drying experiment was conducted on four tropical plantation grown Eucalyptus species （Eucalyptus citriodora, E. grandis, E. urophylla×grandis and E. exserta） for one year to determine their respective air-drying characteristics and rules during the four seasons. The drying rates and the drying defects of the lumber, with respect to different moisture stages and different seasons, were analyzed in this （paper.）These results will provide references for manufacturers on how to make efficient utilization of air drying and kiln drying.