Abstract: The structures and performances of the native kapok fibers were studied.The kapok fiber has thin wall and huge lumen,the hollow ratio can reach 97%.One end of the fiber tapers to one point and is closed,and the other end is bulbous shape and may be closed tightly.The bulk density of the fiber is 0^30 g/cm3.The kapok fiber mainly consists of cellulose and lignin,the crystallization degree is 35^90% and the specific birefringence is 0^017.The structure of the cell wall is looser than that of cotton.The fiber is good heat-resistant,which decomposing temperature is 296 ℃. The fiber stops decomposing and happens carbonizing at 354 ℃.