Trace element geochemistry  of crude oil can be used in oil-source correlation. The correlation parameters can be mainly divided into three categories: ①cluster analysis of trace elements and its indicated general distribution of the elements; ②composition of different families and types of elements, metal elements of transition family in particular; ③rare earth elements. However, there are many uncertainties in this research field. For instance, which elements can be used in oilsource correlation? Which elements have general implications and can be applied to different areas? What factors controlling the effectiveness of the application and how about the main controlling factors? As a consequence, many understandings are preliminary and the successful applications are relatively less in comparison with the application of conventional organic geochemical studies. Trace elements of crude oil are mainly derived from external environment of oil formation and migration and accumulation. In the process of oil generation, migration and accumulation, the trace elements accumulate in oil  by various ways, e.g., metalloporphyrin chelate compound, organic complex compound and adsorbed matters. This takes place through complex organic-inorganic interactions between reservoir hydrocarbons and water and rocks, with the elements dominantly accumulating in asphaltene. In these processes, trace elements of oil differentiate. Moreover, the elements can also differentiate in the formation and evolution of oil, being influenced by the primary organic matter type and maturity and secondary alterations of oil source. These all lead to the heterogeneity of element composition of oil due to different geochemical natures of the elements. The elements that have no or few changes are good parameters for oil-source correlation. This is the principle and theoretical foundation of the application of trace elements of crude oil  to oil-source correlation.