The invention discloses a flexible film laser cladding reinforcing method of a die-casting die. The method includes the steps that the die-casting die is detected comprehensively, and the abrasion loss of the die is determined; a surface fatigue wear layer is removed, and machining surface impurities are removed; alloy powder is prepared, the alloy powder is prearranged on the surface of the to-be-clad die-casting die, a prearranged flexible film is scanned through a laser, and a wearproof laser cladding layer is prepared; and the surface of the cladding layer is nondestructively detected, andthe cladding layer is ground and polished. By means of the method, the utilization rate of the powder in the cladding process is increased, it is guaranteed that the powder is uniformly conveyed, thereinforcing cost is reduced, and the service life of the repaired die-casting die is prolonged by one time or above compared with a conventional repairing method.