Based on the sequence stratigraphy principle, reservoir forming elements has been detailed analysis in Cretaceous system of Hailaer basin, by using core, logging and 3-D seismic data. The study shows that the thick mudstone layer in the transgressive systems tract of the super-sequence is good regional source rock .and regional caprock, meanwhile the sandbody developed in transgressive systems tract and highstand systems of the super-sequence become the regional reservoir of depression. The main hydrocarbon migration pathway is uncomformable surface, fault, frame-sandstone, or that the hydrocarbon born in source rock went into the sandstone of sublacustrine fan directly, and then, lithologic reservoirs was formed.