Abstract: Using the IHS energy information database, we reestablished the prototype basins of Australia northwest passive margin and its palegeography in this paper. The distribution pattern and key factors of 20 giant gas fields are studied. During C₃-J periods, rifts controled the distribution of source rocks. Large scale of deltaic sedimentation in the interval not only brought in a great deal of Type III source rocks, but also provided the most important reservoirs. At the same time, some uplifts and anticlines were formed for accumulation of natural gas. If there is direct seals of marine Cretaceous shale, large gas fields will be formed. It is, therefore, concluded that there is great gas potential in this region.The rift sequence in deep water more than 600 meters is a promissing exploration target.