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Through an integrated study of Mesozoic and Palaeozoic petroleum geology in southern China and a summing-up of the results of exploration, the authors tentatively put forward a set of methods of studying petroleum systems in modified residual basins or superposed basins. Its core idea is to put emphasis on the study of the dynamic evolution of petroleum systems. The tempo-spatial evolution, hydrocarbon-generating processes and hydrocarbon-generating intensities and amounts of resources in different geological stages of chief source rocks are mainly deduced backward by 3-D basin modelling. The regularities of formation and destruction of oil and gas accumulations are summarized by analyzing the fossil and existing oil and gas accumulations, the direction of migration is studied by palaeo-structural analysis, and the dynamic evolution of Palaeozoic and Mesozoic petroleum systems in southern China is studied according to stages of major tectonic movements. The authors suggest that the realistic exploration targets of Palaeozoic and Mesozoic petroleum systems in southern China are secondary and hydrocarbon-regeneration petroleum systems, while the existing primary petroleum systems are rare. They propose that the favourable areas for exploration of Palaeozoic and Mesozoic petroleum systems in southern China are the front area of the Daba Mountains and the steep anticlinal zone on the western side of the Shizhu synclinorium in northeastern Sichuan, the Funin-Yancheng-Hai'an-Xinghua-Baoying area in the northem Jiangsu basin, the Qianjiang-Xiantao-Paizhou-Chacan 1 well area in the southern part of the Chenhu area of the Jianghan basin, the South Poyang basin in Jiangxi and the North subbasin of the Chuxiong basin. This view has been supported by the discovery of the Zhujiadun gas field in the Yancheng subbasin of the northern Jiangsu basin and the Kaixiantaixi oil-bearing structure in the southern part of the Chenhu area of the Jianghan basin.