Abstract: The most suitable centrifugal force to calibrate the T2 cutoff of volcanic gas reservoir rock in Jilin,Daqing and Xinjiang and the low limit of centrifugal force for the movable fluid is 2.76MPa,which is determined by nuclear magnetic resonance（NMR） technique and laboratory experiment on centrifugal force of fluid.The low limit of throat radius for movable fluid is 0.05 μm which is figured out according to the capillary law.There is no obvious functional relationship between T2 cutoff and porosity or permeability of volcanic rock.The research indicates that the range of the T2 cutoff value is very wide and there is a big difference between the T2 cutoff values of different regions or lithologies.But the relationship between T2 cutoff and porosity or permeability of Jilin tuff or Xinjiang graniteporphyry is a little obvious.The order of the T2 cutoff value for the movable fluid of different regions is as follows:Daqing，Jilin and Xinjiang.The average of the T2 cutoff value of rhyolite sampled from Daqing is the largest one and that of Xinjiang basalt and andesite is the smallest one.

Key words: low permeability, nuclear magnetic resonance, T2 cutoff value, centrifuged laboratory experiment, volcanic gas reservoir, lithology