The quantitative relationship between porosity caused by en-trapped gas and mechanical properties of ADC12 alloy has been calculated.The ADC12 plate castings were produced with different injection velocity.The mechanical properties of the samples cut from different position in the plate castings were tested.The volumetric fractions and maximum size of porosities induced by entrapped gas were quantitatively measured by the Arkimeters and image quantitative system to understand the effects on the mechanical properties of the castings.The quantitative relationship between mechanical properties including tensile strength and elongation and porosity fraction as well as maximum size of ADC12 die castings was proposed by the multivarient linear regression method.It was found that the fraction and maximum size of porosities should be controlled less than 4.3% and 180μm in the ADC12 die castings

respectively.