An efficient method to analyze a low-aspect-ratio composite wing with a control surface is developed in this paper. To reduce the problem size and the computational cost, two special schemes are applied. The first is an equivalent-plate methodology and the second is an expanded type of component-mode synthesis. An equivalent-plate analysis was adopted for a semimonocoque main wing, which consists of skins, spars, and ribs, and a thin solid control surface. The main wing and control surface were connected by torsional springs, and the expanded component-mode synthesis was used to combine these two separate components with torsional springs. The first-order shear-deformation theory of plates was the basis of the present equivalent-plate analysis, and a finite element method was applied to solve it. To validate this development, a free-vibration analysis for a cantilevered plate with torsional springs was conducted. Various semimonocoque wings were analyzed, and the results were compared with those using MSC Nastran. A further complex three-dimensional analysis for a composite wing with a control surface was then conducted. The results were compared with those obtained from MSC Nastran to demonstrate the levels of accuracy and the reduction of the problem size.