A semi-analytical methodology on the sound transmission of stiffened laminated plate under different reinforcement forms is developed to explore its sound insulation performance under the action of a plane sound wave load, in accordance with the classical laminated plate theory and in consideration of stiffener flexion and torsional motions. The formula of acoustic transmission loss is obtained by utilizing spatial harmonic expansion and the virtual work principle. Subsequently, the predicted values of proposed methodology are validated by the existing models. Eventually, some characteristic parameters are considered to investigate their effects on sound insulation behavior.