For the structure design of the display unit in civil aircraft cockpit, considering quickness and convenience of display unit removal and installation during flight line maintenance in operational phase, from the point of maintainability design, based on maintainability quantitative requirement and maintainability qualitative requirement of the display unit, the positive design assessment model of removal and installation was proposed, which included the work timeline and process of the design assessment for removal and installation. An example is applied to explain this process to demonstrate the validity of this method. This proposed model can provide strong technical support to the development work of civil aircraft display unit and similar equipment.