Abstract: Nitrogen adsorption is more effective than transmission electron microscope(TEM) in the study of pore structure of cotton fiber.It can be applied to a lot of samples,and more information of pore structure parameters can be acquired.By use of nitrogen adsorption isotherm and of density function theory(DFT) analysis,the pore structures of cotton fiber,such as micropore volume and pore size distributions,were characterized.The results show that cotton fiber contains open pores,the maximum value of pore size distribution appears at 2.2 nm.The pore volume with diameter ranging from 2.0 to 4.0 nm makes up 68.16% of the total,and larger than 5.0 nm,18.49%.