Abstract: PAN fibers with different drawing ratio and different preoxidation degree were investigated by means of sound velocimeter and X-ray diffraction meter.The experimental results show that the sound velocimeter is a very convenient and applied instrument for measuring overall orientation degree and preoxidation degree of PAN fibers,and can be used to study the orientation degree in amorphous region of PAN fiber associating with X-ray diffraction meter,and has the same effect on measuring preoxidation degree of PAN fiber with X-ray diffraction meter.