Due to the existence of multi-fracture and the extension in volcanic gas reservoirs, the success ratio of stimulation is very low as well as the stimulating scale. Based on the unique simulation model for fracturing development and growth during the stimulation, some important topics were studied: (1) the effect of the natural micro-fracture and stimulating parameters vs. the formation and extension of the stimulated fractures. (2) The magnitude of the affecting by different characters of the natural micro-fracture in the reservoir vs. the scale and success ratio of treatments. A new method was summarized to determine the operation indicators in real time on site. And this paper also introduced a series of main fracture controlling technique including: plug with rubber plug, plug with silty sand, displacement compensation at far end of the wellbore, etc. Two logging data from two wells in a large-scale stimulating process are presented in this paper, which proves the necessity and validity of the studying for the main fracture controlling technique in volcanic rocks. This method can also be used as a good reference for stimulation in the similar gas reservoirs.