The tight sandstone gas reservoirs affected by volcanic activity are a special type of tight gas reservoir.Taking the Dehui fault depression in the south of Songliao basin as an example, this paper studies the characteristics of volcanic activity, the deposition of tight sandstone under the influence of volcanic activity, the characteristics of reservoir and the main controlling factors of enrichment by comprehensive application of core analysis, logging, seismic and testing data. Based on the study of volcanism and volcanic facies, sedimentology, lithology and physical characteristics of sandstone reservoirs are studied. It is shown that the fan delta front is the favorable reservoir facies belt, and a classification standard for tight sandstone reservoirare proposed. Based on the analysis of the general characteristics of tight gas reservoir in the Dehui fault depression and the analyses of typical tight sandstone gas reservoir, it is considered that volcanism has an important influence on the formation of natural gas, the temperature pressure system of gas reservoir, and the time of gas reservoir formation. It is mainly manifested in four aspects: ①In the late stage of volcanic activity, the formation temperature and pressure are increased, and the generation and expulsion of hydrocarbon are promoted; ②Volcanic activity affects the sedimentary filling of lake basin, controls the distribution of reservoir, promotes the development of high- quality reservoir, and provides a good reservoir space for gas accumulation; ③The early and middle stages of volcanic activity played a “wrapping role”, that promoted the formation of traps; ④The time space allocation of volcanic activity and regional hydrocarbon generation and expulsion periods is good, which ensures the accumulation and enrichment of tight sandstone gas. These insights are of fundamental significance for studying the formation and distribution of tight sandstone gas reservoirs.