Abstract: Based on the optimization design of ship structure, in view of the current situation that the structural safety margin is too high and the stiffener of stiffened plate is over matched, the concept of the critical stiffness of the stiffener matching was proposed, and the relationship between the stiffness ratio of plate and stiffener was derived. The optimization model of T-type composite stiffener was established. Based on Isight software platform, sensitivity analysis of design variables was carried out to simplify design variables. The Multi-Island genetic algorithm was used to carry out the multivariable optimization design of stiffener. Then, combined with the engineering practice, the design scheme was determined on the basis of the stiffener optimization results. The feasibility of the multivariable optimization design method was verified by the experimental study on the mechanical properties of composite stiffened plates. Research shows that the stiffness ratio formula of the stiffened plate can be used to guide the design of stiffener stiffness matching. In the optimization design of T-type composite reinforcement, the effect of web height on the optimization target is the most obvious. Under the condition of equal stiffness constraint, the optimal design scheme of T-type stiffener can achieve the optimization goal and ensure the better economy.