In this paper the charge transfer and variation of potential distribution upon formation of 4, 4’-bipyridine molecular junction have been investigated by applying hybrid density-functional theory (B3LYP) at 06 initio level. The numerical results show that there exist charge-accumulation and charge-depletion regions located at respective inside and outside of interfaces. The variation of potential distribution is obvious at interfaces. When distance between electrodes is changed, the charge transfer and variation of potential distribution clearly have distance-dependent performance. It is demonstrated that the contact structure between the molecule and electrodes is another key factor for dominating the properties of molecular junction. The qualitative explanation for experimental results is suggested.