Abstract: The influence of pin-fins diameter of minimum elements in the leaning vent hole lamilloy upon the flow resistance and heat transfer was studied through numerical simulation.A locally increased grid density was applied to the bigger area of flow angle with the help of unstructured grid method.k-ε model equation was used to resolve the steady lamilloy along with fixed wall function.The coupling heat transfer was calculated using fluid area and solid area coupling solution.The calculated results were presented,helping to analyze the flow and heat transfer.The research results show that,proper increase of pin-fins diameter is helpful to decrease the flow resistance and increase the cooling efficiency.