Considering the connections between frame and skin of composite rudder, two types of T connections were designed to test the ultimate load carrying capacity when suffering to wave load. According to the load characteristics of structure, a typical local experimental model was extracted, and the load equivalence method was proposed as well. The difference of load characteristics of two types of T connections was compared, and the effect of span on initial stiffness, ultimate failure load and ultimate bearing moment were studied. The results show that type A has obvious initial failure, but the ultimate failure load is larger than that of type B, the ultimate bearing moment does not change with the span, and can be evaluation criterion for different span and different types of T connections. The evaluation method for bearing capacity of T connections was proposed based on the experimental results, load equivalent method and shrinkage principle.