The invention discloses a method for manufacturing a die casting die core. In order to solve the problem of difficulty in heat elimination of an elongated wrapped core in the die casting die, a double-layer composite material core is manufactured, wherein the inner layer is made of pure copper with high heat conductivity, and the outer layer is made of refractory erosion-resistant die steel or refractory steel. The double-layer composite structure is made by using a flame hot spraying method, a laser cladding method and an inserting method. Compared with the H13 die steel core, the surface temperature of the bimetal core of the invention is reduced by about 40 DEG C, and thus, the invention can effectively increase the cast yield, reduce the cooling time and enhance the production efficiency of die casting.