The invention discloses high-heat-conductivity high-corrosion-resistance cast aluminum alloy and a preparation method thereof. The high-heat-conductivity high-corrosion-resistance cast aluminum alloycomprises the raw material components of, by weight, 7-9% of Si, 0.6-1.0% of Fe, 0.2-0.6% of Zn, 0.1-0.5% of Co, 0.05-0.15% of B, 0.2-0.5% of RE, 0.05-0.2% of Sr and the balance Al. In the preparationprocess, the aluminum alloy containing the elements of Si, Fe and Co is melted at the high temperature at first, and then is subjected to still standing and cooled; pure Zn, Al-RE intermediate alloy,Al-B intermediate alloy and Al-Sr intermediate alloy are added into the melt for further alloying; and the melt is subjected to refining and slag removal, and molding is achieved through casting. According to the alloy preparation process, the technology effect is remarkable, the Co, B, Sr and RE multi-element compound synergistic effect is sufficiently realized, and thus, the alloy casting piecehas the excellent heat conductivity, high mechanical property and good corrosion resistance.