Objective: The optimal design scheme of box grid magnetic iron-separator in milk powder production process was explored. Methods: In this study, the working principle of the box grid magnetic iron-separator was explored by using the finite element simulation analysis method under real production conditions in a fully simulated milk powder plant. Through the single factor test, the effects of material drop height, the type of metal foreign matter, the field strength, and the net distance of the magnetic bar on the effective interception rate of the box grid magnetic iron-separator were explored, and the design solution was optimized by using matrix analysis. Results: Assuming that the minimum acceptable standard is an effective interception rate greater than 80% for cast iron, 304 stainless steel and 316 stainless steel, the critical design conditions are as follows: ① When the magnetic field strength of the magnetic bar is 1.0 T, the drop height should be less than 100 mm, the number of layers of the magnetic bar should be greater than or equal to 6, and the clearance of the bar magnet is 25 mm. ② When the magnetic field strength of the magnetic bar is 1.4 T, if the falling height of the material is less than 100 mm, the number of layers of the magnetic bar should be greater than or equal to 4, and the clearance of the bar magnet is 25 mm; If the falling height of the material is between 100 and 300 mm, then the number of magnetic rod layers should be greater than 6, and the clearance of the bar magnet is 25 mm. Conclusion: The research results have industrial application value for milk powder and other powdered food materials, such as protein-based raw materials, powdered fats and oils, starch, food additives, etc.