The purpose of the present study was to discuss the effects of local solidification time and solidus velocity on porosity formation in high strength aluminum alloy casting. With systematic change in the riser size, together with variation of thickness and length, A201 aluminum alloys were cast in 100% silica sand molds. The porosity content of A201 aluminum alloy was affected by the local solidification time and solidus velocity in this study. The correlation between porosity content and solidification time is found to be split into 2 bands, each being associated with one of the two thicknesses of plate castings. The longer the solidification time, the more the porosity content was measured in the A201 aluminum alloy plate casting. And the faster the solidus velocity, the more the porosity content in this study. The porosity content of A201 aluminum alloy was influenced by both of solidification time and solidus velocity at same time in this study. Basically, shorter local solidification time with slow solidus velocity seems get lower porosity content in A201 aluminum alloy castings.