Abstract: A new non Newtonian fluid model was adopted to deal with the non Newtonian performance of the lubricants under the condition of EHL. A modified Reynolds equation was established according to the EHL theories. Numerical calculation was carried out under isothermal EHL condition. On the basis of isothermal solution, the temperature rising profile was analyzed. It has been found from the result of numerical analysis that the shearing stress is affected by slide/roll ratio and the parameter of model, so that the thermal EHL calculation should be carried out under large slide/roll ratio and model parameter. It has also been found that non Newtonian fluid model is applicable to the numerical calculations for both isothermal EHL condition and thermal EHL condition