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Based on the discussion of relationships between thinning and wind damage,and published information, a method for estimating risk ratios of wind dama ge was developed. Estimations of risk-ratio for Pinus thunbergii trees and stand s were deduced from stem bending theory and coefficients characterizing wind pro file, distribution of branches and optical stratification porosity. The results showed that if the value of constant ( in the branch distribution-model equals t he attenuation coefficient αs in the wind profile model for a single tree crown , then the parameter H/D1.33 (height over stem diameter cubed) can be used to co mpare and evaluate the risk-ratio of wind damage for individual trees. The same method can be applied to stands using the coefficient of wind profile in a stand , I.e. Attenuation coefficient α, the coefficient from distributions of optical stratification porosity, I.e. Extinction coefficient ν, and the parameter D1.3 3. The application of parameter H/D1.33 and the process of determining risk rati os of wind damage for stands were also given in the paper.