The Molecular Dynamics Method with the Finnis Sinclair many body potential is used to calculate the formation energies and combination energies of some small vacancy clusters with different configurations in TiAl. The most stable configuration of a vacancy cluster and its effect on vacancy migration nearby the cluster are simulated and discussed. The results show that, in the most stable configuration, each vacancy makes its best endeavor to form nearest neighbor relationship with the other vacancies, and there are anti site defect nearby the cluster. The atoms nearby the vacancy cluster would move towards the cluster center for bigger cluster, and it seems that there exist interstitials in the vacancy cluster. The existing vacancy cluster as the aggregation center of vacancy has the ability of trapping or absorbing the near vacancy.