This paper analyzes the Upper Palaeozoic gas accumulations and conditions of the study area by using the definition and method of petroleum system, and summarizes the natural gas accumulation pattern. The Upper Palaeozoic natural gas in the Yimeng uplift is mainly from source rocks of Taiyuan and Shanxi Formations in the southern part and Wushenqi area. Oil source, reservoir and seal rocks form a good relationship in time and space and they form two types of assemblage which are the self-generating and self-preserving assemblage in the southern part of the Yimeng uplift and the lower-generating and upper-preserving assemblage in the southern and northern parts. Natural gas migrated to the north through the migration pathways composed by advantageous sandbody, unconformity, faults and cracks.