The invention relates to a preparation process of a dual-metal engine cylinder composite material, the preparation process comprises the following steps of: firstly, acid-washing a HT250 cast iron cylinder liner and carrying out surface degreasing and derusting treatment on the HT250 cast iron cylinder liner; then dipping the HT250 cast iron cylinder liner into a prepared proportional saline solution, so that the surface of the HT250 cast iron cylinder liner is soaked in the saline solution; then drying the HT250 cast iron cylinder liner, and putting the HT250 cast iron cylinder liner in a ZL101A aluminum alloy melt body for hot immersion plating; fixing the immersion-plated HT250 cast iron cylinder liner in a mold cavity of a metal mold casting mold, casting, melting and cooling a ZL101A aluminum alloy, wherein concentration of the saline solution is 100-200g/L, the saline solution is prepared by mixing water together with potassium fluoride KF, potassium chloride KCl, sodium chloride NaCl, calcium fluoride CaF2, and calcium chloride CaC12 according to a mass ratio of 39-46:16-26:15-21:6-15:5-10. According to the preparation process, the engine cylinder composite material is obtained through treating the ZL101A aluminum alloy and HT250 cast iron by a self-prepared surfactant and implementing a dual-metal composite casting process on the ZL101A aluminum alloy and the HT250 cast iron, wherein two metal materials of the ZL101A aluminum alloy and the HT250 cast iron are not mixed and kept with original physical properties; but the ZL101A aluminum alloy and the HT250 cast iron obtain an extremely perfect combination interface, so that casting metallurgical bonding of 99.5 percent and above is achieved.