Abstract: Upper Cretaceous is the main formation of Mesozoic and plays an important role in oil and gas exploration in Subei Basin. Two reservoir formation models have been found in Subei Basin:one is "old-generating and new-accumulating" and another is "new-generating and old-accumulating", and the typical fields are Chenbao Oilfield (of the latter model) and Zhujiadun Gasfield (of the former model). This article discusses these two reservoir formation models and gives a prognosis of Cretaceous "self-generating and self-accumulating" model according to the analysis of two Cretaceous reservoirs. In the meantime, the paper analyzes the exploration factors of three models, and gives the opinion that the "old-generating and new-accumulating" model is the most important target in the future.