Abstract: The faults in the block A of Northeast Ordos Basin are divided into two types, i.e. volcanic activity related faults and regional stress related faults, according to their origin. The volcanic activity related faults by Z magmatism destroy gas accumulations. However, the regional stress related faults, which are influenced by L sinistral strike-slip and composed of northwest tensional strike-slip faults, northeast and near north-south compressional strike slip faults and X type conjugate shear fracture faults, are favorable to gas accumulation. Within a radius of 2 kilometers surrounding the regional stress related faults, gas can get better accumulated. These research results challenged the old view point that the sedimentation was the only influence factor in tight gas accumulation. It means that fault genetic mechanism and its controlling over gas accumulation possess plays key roles in oil accumulation and have great significance to the exploration and development of the Upper Paleozoic tight gas in northeast Ordos Basin.