Abstract: The paper is based on the Bayes statistical theory to conclude the principle and method by using Monte Carle computer similation technique,structuring the reliability maximal entropy distribution under the function parameters of mechanical stress and strength.This method,by means of the counting example analysis of the cylindrical spiral spring reliability,has shown that it has the applied value in machine engineerings,and can also provide a tentative tool and theory for determining the united formal theory of distribution kinds, to calculate mechanical reliability in machine engineering area in the future.