To fit the special needs of gray cast iron as a new engineering material,i.e.,higher σ b and lower HB,or lower σ b and higher HB,using the method of heat analyzing and polyparameters analytic figures,the synthetic rules of carbon saturation degree,inoculation degree and mechanical properties can be exposed.The result shows that,according to the needs of the part′s mechanical properties,referring to the synthetic rules of gray cast iron,the corresponding technological measure and composition proportion can be defined,by which we will get the exact mechanical properties that could achieve the result expected completely.Thus,the casting for gray cast iron might be 'designed'from'selected'.