The fracture behavior and failure strength of carbon fiber composite T-joint under tensile condition were predicted numerically, and the predicted results were compared with the test data. In the numerical model, the initiation and propagation of the filler cracks and interlayer interface stratification in the T-joint triangle region were considered by using the augmented finite element method (AFEM) and the cohesive zone model respectively. The results show that the numerical results are in good agreement with the experimental results, and it can be found that the crack initiates in the triangle region of the T-joint structure. The fracture behavior of the filler does not affect the ultimate failure load of the T-joint. The delamination behavior between stiffened laminates and skin laminates is responsible for the final failure of the T-joints.