In this work, PAN fibers web was fabricated by Electrospinning, and then was pre-oxidated. Effect of the temperature on the structure and property of pre-oxidation web was discussed. The results showed that better level of pre-oxidation nanofibers web can be obtained when the pre-oxidation temperature is 250 degrees C. At this temperature, Infrared Spectroscopy showed that cyclization and dehydrogenation reaction have occurred and DSC curves showed that cyclization was basically complete, as well as moisture content can be appropriately controlled. Moreover, the preoxidated web with better breaking strength, elongation at break, and the initial modulus could be obtained.