We have determined sets of coarse-grained potentials for nCB (4-n-a1kyl-4 ' -cyanobiphcnyl) starting from the united atom pair potential of the OPLS force field. As a coarse-grained model, we employed a hybrid Gay-Berne/Lennard-Jones model consisting of a rigid core and a chain of spheres. Using the coarse-grained potentials, we have carried out MD simulations of 5CB to examine the parameter dependency of the structure, the density of the ordered state and the transition temperature. We found that if the length of the rigid core is kept constant, the isotropic phase becomes favored with increasing the aspect ratio of the core. This can be explained as the effect of the thickness of the tail part.