The Bohaiwan basin is a petroliferous basin superpositioned on the Huabei platform. With petroleum exploration growth, coal-derived gases generated from Carboniferous-Permian source rocks have been found in many places in the basin. By geochemical investigation the authors believe that the gases are products of secondary hydrocarbon generation after Palaeogene, which can be accumulated in traps, and find that present low-uplift, slope and sag areas are favorable for the gas accumulation. As faults are developed everywhere, the coal-derived gases migrate up to Tertiary and mix with oil-type gases generated from the Shahejie Formation source rocks. By statistics of carbon isotope compositions of methane and ethane in natural gases generated from types I, II and III of organic matter, the authors postulate two plots for identification of the oil-type gas and coal-derived gas, their mixed gas. By application of one order chemical kinetics, the productions of coal-derived gas secondarily generated from C-P source rocks are estimated for five different structural units. In conclusion, there are no secondary gas generations in the rise unit and uplift unit where no coal-derived gas accumulates. The gas production is over 80% from the resource rocks in sag belt unit which is a good gas kitchen for overlain traps. Coal-derived gases and light oils are quickly generated from the C-P source rocks in the slope and low-uplift units, where are favorable for gas exploration. This paper is useful in understanding coal-derived gas accumulation and exploration in the Bohaiwan basin.