Abstract: The effects of ultrasonic treatment on the morphology,crystalline morphology,thermal performance and mechanical properties of cotton fibers were tested and investigated through X-ray diffraction(XRD),thermal gravimetric analysis(TGA),scanning electron microscope(SEM) and etc.with an attempt to set a theoretical basis for the application of ultrasonic treatment to dyeing and finishing of cotton fabrics.The experimental results indicated that ultrasonic treatment alters the morphology of cotton fiber,makes the natural curvature inherent to the fiber disappeared and the fiber surface rougher.The crystallinity and crystal size decrease and the thermal stability falls due to its reduced thermal pyrolysis temperature.Moreover,its breaking strength is reduced but the breaking extension improved.