Abstract: The reservoirs in South China are characterized by mixed-sources,multiple kitchens as well as multi-stages of accumulation,deformation and destruction.It is necessary to explore new description methods and research ideas of petroleum preservation studies.A new concept of 'preservation system' and its research methods were put forward in this paper.The 'preservation system' is a unity of geological factors,geological functions and processes,and reservoir formation associated with preservation conditions in a geological unit.This system has an integrate source-cover condition,the same or similar geological structure and fluid characteristics,and the consis-tent preservation(or destruction)process of oil-and-gas reservoir.A preservation system is an oil-and-gas exploration unit,and its scope corresponds to a second-class or a third-class tectonic unit of a basin.The study content of the preservation system includes 4 basic features(geological structure types,cover functions,source-cover dynamic relationships and fluid characterizations)and 1 comprehensive evaluation system.The new concept and research methods may meet the needs of oil-and-gas explorations in South China or similar polycyclic basins.