A method for preparing an alloy encapsulation mobile phone protective case is provided, which includes steps of: selecting an alloy material as an edging material; CNC machining; making a surface treatment; drying; spraying and molding for shaping. The alloy encapsulated mobile phone protective case is formed after shaping the alloy outer frame and the soft rubber inner molding layer, which not only simplifies the assembly, but also strengthens the strength and hardness of the structure, thus effectively avoiding the splitting phenomenon caused by strong impact. Due to the combination of the alloy material with the soft rubber inner molding layer, the protective case has a certain flexibility, abrasion resistance, high strength and high formability. The rigidity of the protective case is in a range from 50° to 90°and has strong resilient force and curvature, which not only can effectively protect the mobile phone, but also has long service life.