Polarization imaging techniques are capable of probing the structural and optical properties of anisotropic turbid media. These techniques are compatible in optical layout with the corresponding none polarized optical techniques, but can provide far richer micro structural information of the complex samples, especially the structures in the sub-wavelength scale. As a label-free, non-destructive method, polarization imaging has shown many potential applications in biomedical studies and clinical practices. In this paper, we present a brief introduction on different existing polarization imaging techniques including the difference polarization (DP), degree of polarization (DOP), rotating linear polarization imaging (RLPI), polarization microscopy and Mueller matrix imaging. Moreover, we summarize the recent progresses of these polarization imaging techniques being applied in biomedical studies and clinical practices, such as detection and diagnosis of different cancers. The Mueller matrix provides the comprehensive representation of the polarization properties which are closely linked to the micro structure of the tissues. We present the recent studies in Mueller matrix polar decomposition (MMPD) and Mueller matrix transformation (MMT) to extract from the Mueller matrix elements groups of new polarization parameters with clearer physics meanings or more explicit connections to the structural features. The MMPD parameters, which reflect the depolarization, retardance and diattenuation properties of samples, and the MMT parameters, which are closely related to the anisotropy and density of sub wavelength small scatterers, are applied to characterize the distinctive features of human skin basal carcinoma, papillary thyroid carcinoma and cervix cancer in clinical samples. With the rapid technological advances in the light sources, polarization modulation optics, detectors and processors, polarization imaging devices are likely to be made smaller, faster, cheaper and easier to operate, which will open up new frontiers in biomedical studies and clinical applications.