The samples this thesis investigated were m-plane nitrides films grown on m-plane sapphire by plasma-assisted molecular beam epitaxy (PAMBE). Scanning electron microscopy (SEM) images revealed the surface morphologies of the films and thicknesses of the films were measured by cross-sectional scanning electron microscopy. Then we used electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) to check the growth orientation of the films. The m-plane nitrides films have the anisotropic optical properties were due to the growth orientation of the films. The films are under anisotropic stress since they were grown along m-axis and hence change the electron band structure (EBS), which resulted in anisotropic optical property. We studied the polarization properties of the luminescence at 15 K and 300 K by polarization dependent photoluminescence (PL) and calculated the degree of polarization. And then measured the strain of the m-plane nitrides films by micro-Raman spectroscopy, discussed the degree of polarization and stress. The degree of polarization larger as the anisotropic stress of the film increased.