Nematic-Isotropic (N-I) phase transition is discussed in an alternative way by using Landau-de Gennes phenomenological theory. The temperature difference of TNI - T* is obtained near the tricritical point. We also obtained the value of the ratio (Q* -QNI)/QNI, where Q* is the order parameter at the temperature T* of the absolute stability limit of the isotropic phase and QNI is the order parameter at the nematic-isotropic transition temperature TNI.