The three dimensional finite element model of composite laminates made of carbon fiber reinforced bismaleimide resin is built, and the stress state of the composite laminates under unidirectional tensile force is presented based on finite element analysis. The strength criterion and initial damage mode are given based on the stresses of material principal direction. The three dimensional finite element model of the same laminates with non-penetrating damage repaired by scarf bonding method is built, and the stress state is also analyzed. Annular solids are used to simulate the resin between the mother laminates and the patches. The strength criterion and the damage mode of the scarf bonding composite laminates are also given. The strength and the damage mode of original laminates are compared with that of the repaired laminates. The influence of the annular shape resin is considered in the repaired model. It is showed that the three dimensional models can simulate the geometric and physical features of the real composite laminates. It is concluded that the original composite laminates and the repaired one both damage first in the laminar whose second material principal direction coincides with the axial tensile force. And the damage mode is resin crack under tensile stress. The strength of the bonding patches is higher than the repaired laminates. After scarf bonding repairing, the strength of the damaged laminates can recover up to about 88%.