Embryos excised from wheat (Triticum aestivum) grains following gamma-ray irradiation at different doses were analyzed on membrane permeability by electron paramagnetic resonance (EPR) technique with 4-oxo-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPONE) as spin probe to acquire an EPR spectrum. The broadening agent ferricyanide added leads to changes in the high-field region of the EPR spectrum, which reflects differences in membrane permeability. R-value, defined as the ratio of water (W) to lipid (L) component in height in the high-field region of the EPR spectrum, symbolizes membrane permeability for a given sample. The R-values corresponding to a certain dose treatment of grains displayed a definitive distribution pattern. A unit row vector with 20 components was used to describe the R-value distribution pattern for a given treatment. The transaction angle between vectors corresponding to grains irradiated and unirradiated, θ, was used as quantitative index for membrane permeability changes following gamma-ray irradiation. gamma-Ray irradiated grains germinated at low rates, and the regression equation of germination rate as a function of the irradiation dose is: Germination Rate (%)=94.8 exp[-0.264xIrradiation Dose (kGy)] (r(2)=0.991, P<0.001). Embryos excised from grains following gamma-ray irradiation show increases in θ values with irradiation dose. The θ value is negatively linearly correlated with the germination rate. It suggests that gamma-ray irradiation leading to increases in membrane permeability is consistent with that leading to low germination rate of grains. The introduction to vector analysis method on membrane permeability changes in this study is very practical.