Abstract: Based on the methods of origin and statisticaI modelling in hydrocarbon resource assessment, the method of Pareto truncated distribution modelling is constructed to predict oil and gas field numbers and their size and distribution in a mega-petroliferous region. The degree Of resource concentration is also proposed in this paper as an important parameter in resource evaluation, and the modelling procedure is fulfilled through iterative and approximate algorithm. At last, a case application of the oil resource forecasting of Tarim Basin is presented and the selection of related parameters is discussed.