Abstract: Melting critical condition of aluminum alloy dual sheet subjected to hypervelocity impact was studied experimentally and theoretically. With the help of a two stage light gas gun, LY 12 aluminum alloy samples subjected to hypervelocity impact by the projectile made of LY 12 aluminum with different speeds ranged from 4 to 6 km/s became available. The projectile was 5 mm in diameter. The first plate was made of LY 12 aluminum alloy and 3 mm in thickness. The second plate was made of L 4 aluminum and 3 mm in thickness. A clearance of 120 mm was between two plates. Experiment result showed that 5 km/s is the minimum speed inducing melting of LY 12 aluminum alloy. The theoretical analyses and simulation result gave a powerful support to this point.