It is a critical part at the basic design phase of aircraft structural design to build a finite element model and it will have a direct impact on time and cost for airframe structure development. In addition, the objective of finite element model will be varied depending on each design review phase and the modelling methodology varied accordingly. In order to build an effective and economic finite element model, it is required to develop adequate level of modelling methodology based on each design phase and its objectives. Therefore, in this paper, the finite element modeling methodology was presented for internal load analysis of wing structure of multi-spar type military aircraft, load path evaluation and initial sizing of wing structure. All structures reflected mechanical function and at the same time, idealized to achieve easy and conservative result of internal load evaluation. Through analysis of various loads, it was confirmed that the finite element modeling suggested in this paper and initial sizing method could be applied to internal load analysis of wing structure and initial sizing.