X-ray diffraction and low-temperature nitrogen adsorption were adopted to investigate the pore structure and crystallization property of the fibers of old newspaper pulp（ONP） and deinking pulp with different deinking modes,and the fractal geometry was used to further analyze the pore structure of the fibers.The results indicate that（1） the BET specific surface area,BJH pore volume and BJH average pore size of the deinking fibers remain almost unchanged after a neutral,alkaline or enzymatic deinking process;（2） the fractal dimensions of the fibers before and after the deinking process are similar,which means that deinking modes have little effect on the pore structure of the fibers;（3） the crystallinity of the fibers decreases to 12.24%,6.12% or 0.77% after a neutral,alkaline or enzymatic deinking process,respectively;（4） the water retention value（WRV） increases after deinking,in an order of alkali deinkingneutral deinkingenzymatic deinking;and（5） after deinking,the beating degree and average length of the fibers slightly decrease while the content of fine fibers increases.