Domain is the intrinsic characteristic of all of the ferroic material. The structure of domain and domain wall has significant effects on their physical properties. We’ve investigated the 109o domain wall structure of complicated rhombohedral perovskite BFO thin films at atomic scales by using high resolution electron microscopy and quantitative electron micrscopy. The displacement of cations and local polarization distributions across the domain walls were determined. It reveals that the observed room temperature conductivity at domain walls in the insulating multiferroic BiFeO3, correlates with the structural driven changes, resulting in a decrease in the bandgap at the domain wall. The results would provide quantitative structural information for understanding the the polarization reversing and magnetoelectric coupling in multiferroics, and for the research and development of related devices in electronics industry.