Nanohydrocarbon is a new concept for oil accumulation mechanism, and oil can be found in nanosized pore throats. At Qikau Sag, the source and reservoir are found coexisting along the slopes of this basin. It is a complex process for nanopores to converge into the reservoir. Source-control theory and multiple oil-gas accumulative zone theory are the efficient petroleum exploration theories in the areas of low-middle developed exploration degree in the continental basin, but they are not suitable for middle-high developed exploration areas. For this reason, in this research work, the theory of the Petroleum Exploration System based on main migration pathway and nanohydrocarbon is proposed. In complex middle-high developed petroleum exploration area, we focus on the premise of determining the source and use the abundant data of seismic, logging, coring, analysis and testing, production performance, and a large number of research results of predecessors, to detect the geometry of the main migration channels of oil and gas and to make clear migration trajectory of oil and development history of traps, track clues, and dig the optimization exploration areas based on the assessment condition. The risk for petroleum exploration in a new area can be minimized and led to the utmost advantage of exploration by using this option.