The invention relates to an explosive welding forming method for a magnesia-alumina-titanium alloy composite board, which is performed aiming at the performance requirements of a magnesium alloy board, an aluminum alloy board and a titanium alloy board; an ammonium nitrate fuel oil mixture is adopted for performing remote instant explosive welding forming on a sand substrate on the ground; the welding forming method is quick in speed, firm in interface bonding, good in interfacial shear strength and high in boding rate; the magnesia-alumina-titanium alloy composite board achieves the shear strength of 150MPa, the explosive welding bonding rate is 96.8%, the controllability is good, the welding process is safe and reliable, and thereby the explosive welding forming method is a reliable and effectively method for preparing the magnesia-alumina-titanium alloy composite board.