Abstract: The self-assembly behavior of 4,6,-dichloro-2,5,and-biphenyl pyrimidine(DCDPP) molecules on Au(111) surface was investigated with ultra-high vacuum scanning tunneling microscope for manipulation of self-assembly structure via π-π interaction.The influence of the DCDPP molecular coverage on the self-assembly nano-structures was experimentally measured and theoretically analyzed.The preliminary results show that the molecular coverage made the difference.For instance, the rotating 5-benzene ring in DCDPP molecule was responsible for the π-π interactions; a low coverage of DCDPP molecule self-assembled into stable chains and well-ordered 2 D structures; a higher coverage self-assembled into different high density 2 D islands, possibly because of the localized stress.We suggest that the results be of some basic and technological interest in development of molecular electronic devices.