Abstract: In order to study the casting properties of a new aluminum alloy containing scandium for mechanical end cap, the microstructure and casting properties of the aluminum alloy Al-7Si-0.3Mg-xSc (x=0, 0.1, 0.3, 0.5) with different scandium contents were tested and analyzed. The results show that with the increase of scandium content, the internal structure of the alloy is refined first and then coarsened, and the casting properties are improved first and then decreased. The scandium content of the aluminum alloy Al-7Si-0.3Mg-xSc is preferably 0.3%.Compared with those of the alloy without scandium, the test value of aluminum liquid flow length of Al-7Si-0.3Mg-0.3Sc alloy increases by 12.1%, and the measured value of crack length decreases by 22.4%. The fluidity and hot crack resistance of the alloy are significantly improved, and the casting properties of the alloy are significantly improved.