Abstract: Based on the data of drilling cuttings, cores, thin sections, well logging and others, this paper established a set of template for quantitative identification of volcanic rocks, so as to reveal the spatial distribution pattern of volcanic rocks in the B oilfield of the Huanghekou Sag. According to the rock types and rock association as well as the seismic characteristic of volcanic edifice, we subdivided in this paper six volcanic facies i.e. the volcanic channel facies, overflow facies, explosive facies, extrusive facies, sub-volcanic facies, volcano-sedimentary facies, and related facies associations. Furthermore, a volcanic eruption model is concluded upon above study. There are in fact two eruption models, one is the central vent eruption which is popular in the area of B1, and the other is the crack-central vent eruption represented by the B8 area. The study results mentioned above play important roles in the description of volcanic rocks and the risk evaluation of reservoir, and have made important contribution to reserve calculation of the oilfield.