This study is to explore the void area with surface treatment of fiber. We observed the surface void of fiber by SEM, and changed five kinds of brightness and contract to make the border of void clearly, then picked up the best image to measure the void area. Before measuring the void area, we measured the area on an actual circular hole after five kinds of brightness and contract treatment to compare with the actual area. We can find that the erroneous percentage is under 10% and logarithmic is the lowest, so we measured the void area with logarithmic treatment. The results show that the dimensions of void is micron, and the biggest area of PBO fiber is 0.1188196 μm^2, the smallest is 0.0016175 μm^2. The area of high strength PET is 5.6690271 μm^2L and the area of high strength Nylon is 1.7332084 μm^2.
