Aircraft modular design can increase the types of missions and reduce costs. In the initial stage of wing modular structure design, the unclearness of wingtip deformation limits the ability to assess the contribution differences of structural stiffness characteristics among wings with different spans to the system objective function (minimal structural weight).Aiming at the above problems, this paper introduces the weight coefficients of each subsystem level in the system level on the basis of the sensitivity coordinated optimization method to simulate the phenomenon that different subsystems contribute differently to the objective function of the system in the actual design work, and gives the computation methods of weight coefficients of the wing structures with different spreading lengths (different subsystems levels), forming the sensitivity coordinated optimization method with subsystem level weights. Finally, the preliminary structure design method of modular wing is verified by solving the modular truss and modular wing structure optimization example. The results show that the sensitivity-coordinated optimization method that includes subsystem weights can obtain a modular wing preliminary structure that satisfies both strength requirements and a certain degree of stiffness.