After more than 30 years of exploration for coal gas in Jiyang Depression，breakthroughs have been made in Gubei，Huimin，Linqing，Chexi，and other areas，but large-scale reserves have not been formed. Therefore，it is necessary to further explore the main factors controlling the accumulations of coal gas. Based on the seismic survey，mud logging，well logging，and production test data，the genetic types of the Lower Paleozoic natural gas in the northern steep slope zone in Chexi Subsag，Chezhen Sag，Jiyang Depression（the northwest of Chezhen Sag）. In addition，the differences and main controlling factors of accumulation for the Lower Paleozoic coal gas reservoirs in the study area were analyzed. The results demonstrate that the Lower Paleozoic natural gas in the northwest of Chezhen Sag is coal gas，which mainly comes from thecoal-bearing strata of the Upper Paleozoic，leading to favorable geological conditions for accumulation. The coal-bearing strata have a buried depth generally over 4 100 m and have entered the stage of secondary hydrocarbon generation，and the differences in hydrocarbon generation quantity are determined by their buried depth and thickness. The fault displacement of adjacent faults plays a crucial role in coal gas accumulation：It dominates both trap-source connection and the width of the Lower Paleozoic reservoir，thereby directly determining the effectiveness of the trap. When the fault displacement of adjacent controlled faults is more than 150 m，the Lower Paleozoic trap in the hanging wall can be connected with the Upper Paleozoic source rock in the footwall. The coal gas from the Upper Paleozoic migrates along the fault into the Lower Paleozoic carbonate rock reservoir transformed by the fault，and then accumulates in the favorable trap near the source.