The Daqing volcanic gas reservoir is deep, and the types of reservoir's rock and pore space are complex. The rock is tight and the properties are poor. It belongs to the low porosity and low permeability reservoir. The experiment of stress sensitivity and rock mechanics are done using Daqing volcanic samples to study the rule of the changes of reservoir physical properties in the process of development. The results show that the hardness of Daqing volcanic formation is strong，the compressive strength is high, and the stress sensitivity small. When effective pressure increases from 5 MPa to 60 MPa, the porosity decreases by less than 5% (relative value). But the change of permeability is complex. The decrease rate of porous volcanics is low, just about 10％～20％. The fractures of fractured volcanics will be closed under low pressures. Its permeability decreases quickly, but decreases slowly under high pressures. The total decrease rate of permeability is about 40％～60％. The calculation of one gas field shows that the reservoir's permeability decreases by a small amount when the depletion drive development of the gas field from the initial pressure to the later low pressures. The decrease of porous reservoir is by about 3.5％, and the fractured reservoir by about 17.1％.