The effect of strontium modification and its fading behavior on the microstructure and mechanical properties of the direct electrolytic A356 alloys were investigated. The results show that there exists the interaction between the modification and refinement, the grain sizes are more refined and the second dendrite arm spaces decreased with the increasing of the strontium contents, as well as the effect of modification is better and better. The morphology of silicon is plate-like shape in non-modified and transfer into the fine fibrous coral-like in modified when strontium content is super than 0.01%. The optimum content of strontium is between is 0.02%～0.03%, and the effect of silicon spheroidization is better and the outstanding mechanical properties can be achieved after T5 treatments. The result of fading behavior is that the grain size increases and the effect of modification fads with the prolonging of the holding time. When the holding time exceeds than 150 min , the silicon morphology is turned into non-modified. It may be related to the solution and deposition of TiAl 3 particles and the burning loss of strontium.