The currently most-accepted petroleum resource classification system in the world is PRMS （2007） sponsored by SPE/WPC/AAPG/SPEE. Taking this classification system as a standard, the corresponding relationships of the petroleum resource classification systems among USGS （2000）, IHS （2009）, the new round petroleum resource assessment （2007） in China and PRMS （2007） were analyzed. Petroleum resource was a general concept and had very different understandings in different cases, so a clear concept was necessary. It was advised that a clearly defined petroleum resource potential concept was practically useful to reflect the exploration and exploitation potentials of an assessment unit （region, basin or play）, petroleum resourcepotential of an assessment unit was defined as the amount of technically recoverable oil and （or） gas quantities of the assessment unit from the assessment date to a future time. By comparing petroleum resource classification systems of domestic and foreign institutions, it was concluded that the unproved recoverable petroleum resource of the new round of petroleum resource assessment （2007） could reflect the exploration potential of the assessment unit, the proved remaining recoverable reserve could reflect the exploitation potential of the assessment unit, and their sum could reflect the resource potential of the assessment unit. Meanwhile, the undiscovered recoverable resource of USGS （2000） could reflect the exploration potential, the remaining recoverable reserve of IHS （2009） could reflect the exploitation potential, and their sum might also reflect the resource potential of the assessment unit. The clearly defined concept of the resource potential had an important guiding significance to the resource evaluation data reference of different foreign institutions, in carrying out the petroleum resource evaluation of global basins, for Chinese institutions and petroleum companies.
