This paper aims to evaluate the degree and the number of pile stack between five and six ribs wing box that created from the Eppler 397 Airfoil (e397-il) model. The model was varied three numbers of pile stack and six degrees of angle of pile stack to find the best result for the composite material to construct the High-Altitude Platform (HAP). The thickness of pile was fixed at 0.234 mm. The structure of wing box has the safety of factor 5.7 and receive load 3,052 N. The model was analysed by ABAQUS software to compute the vertical-static such as Tsai-Hill and skin defection that did not exceed 1 for Tsai-hill and 2 mm for skin defection. The results were shown that the wing box had six ribs model with the angle of pile stack as [+45/-45/90/90/0/90/90/-45/+45] was the best model in this research. It had Tsai-Hill 0.030 and skin defection 0.348 mm. The model had more ribs and number of pile stack increase the strength of wing box and the degree of pile stack between the outer and the adjacent layer should be a perpendicular direction.