We present a modified Gay-Berne (GB) potential, in which the attraction force can be tuned by adjusting one parameter only. An attractive parameter Ps is introduced for describing the strength of attractive force relative to its repulsive counterpart between large particles. Using the proposed model, the phase transition phenomena of liquid crystal molecules as the density varies from 0.32 to 0.24, have been investigated. Simulation results are compared with the results of using traditional GB potential. The phases and phase transitions observed by using different attractive parameters show the importance of studying the variation of attractive forces, which resulted in dramatic different phase transition phenomena. (C) 2011 Elsevier Ltd. All rights reserved.