The invention relates to a high-strength heat-resistant cast aluminum-copper alloy with the low porosity and a preparation process. According to the alloy, the higher Ti and B contents, the high V content and the low Zr content are adopted, and the Zr/V ratio is controlled to be less than or equal to 0.625, so that Zr, Ti and B are synergized to refine grains, the interdendritic hole formation iscontrolled, and the heat cracking resistance of V cannot be reduced due to Zr. Meanwhile, during raw material preparation, tool preparation and smelting processes, on the basis of adopting a high-purity argon and intense agitation combination H-removal process measure, through adding trace of rare earth element RE, the content of the melt H is further reduced, the formation of high-strength heat-resistant cast aluminum-copper alloy casting blow holes and pin holes is controlled, and the performance of a large-scale casting body is improved. The preparation process comprises the steps of smelting and casting the alloy, and carrying out solution and aging treatment on the casting. The high-strength heat-resistant cast aluminum-copper alloy with the low porosity provided by the invention canbe used for preparing the large-scale aluminum-copper alloy casting with the low porosity, a dense structure and no heat cracking, and the casting has favorable mechanical property, heat resistance and cutting processability.