Measurement of the fiber composition and content is important for textile testing. At present, the widely used testing methods require complex sample preparation and rely on the subjective judgment, which decreases testing efficiency. The rotating linearly polarized light imaging method is based on multi-incident and detection polarization angles images. By fitting the polarization difference as function of these multi-incident and detection polarization angles, a characteristic parameter related to fiber microstructure is obtained. The common textile fibers can be easily discriminated by this characteristic parameter. Based on the measurement results of single component fiber, it is feasible to detect the component and content of blend fibers by this technique. This technique has the advantage of non-destructive operation, in vivo testing, and rapid speed.