Through the analysis of geochemical characteristics of core samples, it is showed that volcano rocks are mainly basalt and trachyandesite in Chagan depression and the rock type can be identified better by logging crossplot. Based on morphological sign of volcano rock lithofacies, seismic profiles and single well facies, the main facies developed in Chagan depression are determined as volcano channel facies, explosive facies, overflow facies and volcano sedimentary facies. And different rock lithofacies have different type of rock combinations. Drilling data reveal that volcano rock of Su2 has medium porosity and extra-low permeability, which is better than that of Su1 extra-low porosity and extra-low permeability; the petrophysical properties of the volcano reservoir are mainly controlled by fracture development withstrong heterogeneity. Exploration practice shows that the oil and gas accumulations in volcano reservoirs in Chagan depression are characteristic of near-source accumulation, an joint control of good quality reservoir and fracture zone; Uligi structural belt and the central structural belt are favorable areas for oil & gas accumulation, which are near the hydrocarbon generation center and have favorable fractures to increase the reservoir space and facilitate the way to hydrocarbon source rocks.