Abstract: The resolution of evaluation results is sometimes low when using the present gray association analysis to evaluate the geological models of lithology,physical properties,oil potential and oil-bearing area.In regard to this problem,a new gray fine evaluation model has been constructed using the Lagrange multiplier method on the basis of the Jaynes maximum information entropy principle and definition of gray association in the information theory and structural target function.A case study is given to explain how to use this model.A comparison of this new evaluation model with the original gray association analysis shows that their results are in the main consistent and the resolution is markedly raised.This model is strictly derived and has higher sensitivity and reliability.