Abstract: To find out the genesis and distribution of volcanic reservoir in Kalagang Formation of Upper Carboniferous System of Malang sag in Santanghu Basin, from the analysis of the geologic characteristics of volcanic reservoir and the controlling factors of reservoir formation, it is pointed out that the key controlling factors of reservoir formation are volcanic facies, high-quality hydrocarbon source rock, fracture and unconformity. Highquality hydrocarbon source rock of Haerjiawu Formation of Upper Carboniferous System provides rich oil source for the volcanic reservoir of Kalagang Formation, unconformity and widely-developed fractures do not only provide conditions for the formation of volcanic reservoir, but they are the channel of upward migration of lower oil and gas. Further oil and gas exploration should be carried out in the volcanic rock weathering crust development area near aquifer region between the nip-out lines of Permian Tiaohu Formation and Upper Carboniferous Kalagang Formation. The southeast edge of Niudong area, Mabei structural zone, and Madong structural zone are favorable for oil and gas exploration

Key words: Santanghu Basin;Malang sag, Kalagang Formation, volcanic reservoir, key controlling factor