Phase diagrams in mixtures of side chain liquid crystalline polymers (SCLCP) and liquid crystals (LC) have been computed by combining Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe (MS) theory for nematic ordering. In the calculation, two orientational order parameters with two different clearing transitions are taken into consideration for nematic mixtures. In the case of flexible homopolymer and liquid crystal mixtures, only one orientational order parameter with one nematic-isotropic transition is necessary. he effects of molecular weight of matrix polymer on phase diagrams of polymer/liquid crystal mixtures have been investigated using polymethyl methacrylate having varying molecular weights as matrix resins.