The purpose of the present study was to discuss the effects of local solidification time on porosity content of long solidification range A201 aluminum alloy plate castings. With systematic change in the riser size, together with variation of thickness and length, were cast in different kinds of molds. The sand molds with end chill for the plate castings were made of 100% silica sand. The porosity content of A201 aluminum alloy was affected by the local solidification time 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 thickness of plate castings.