The FE modeling of complex trunk structure often needs shell and solid elements. Different commercial software adopts different shell-solid coupling techniques. A simple, robust method has been demonstrated for shell–solid coupling by fictitious perpendicular shell. Systemic study on the method is performed through the FE analysis of T-trunk model to ensure the displacement compatibility and stress equilibrium. Modal analysis of gearbox is executed to observe the reliability and efficiency of the coupling method. Parametrical conclusions and practical suggestions are presented finally.