Temperure dependence of Eaman spectra of nematic liquid crystals MBBA and EBBA made in China is reported. The spectral behaviours of these two types of liquid crystals are quite similar. Separation theory of vibrational and rotational correlation function which could only be applied in isotropic liquid phase is extended to anisotropieally oriented nematic liquid crystals. The experimental results of applying the extended theory to study vibrational and rotational relaxation of molecules in nematic and liquid phases of MBBA show the feasibility of the extended theory.