The AS characteristics are studied in detail for No. 1 Member volcanic reservoir of Yingcheng Formation in Xudong Area of Xushen gasfield of Songliao Basin. The results show that the AS of the target reservoirs in the study area can be divided into 2 types:primary and secondary and 8 sub- classes. The former mainly includes 4 types:gas pore, intergranular pore, intragranular pore and exploded fracture; the later generally contains 4 kinds as well:intragranular dissolved pore, intergranular dissolved pore, structural and dissolved fractures. The 4 AS types are principally developed in the target reservoirs in the study area i.e. pore, fracture-pore, pore-fracture and fracture.