Abstract: The numerical mode of carbon fiber T-joints was built by finite element analysis software, and its cohesive mode technique. The damage formation, extension and failing process of T-joints under tensile load were investigated. Then the static tension test was carried out on the carbon fiber T-joints. The test results demonstrate that the initial damage load was between 9.8 kN and 12.0 kN, and after the damage appeared, the bearing value on the T-joints descends sharply (approximately by 27%-38%). The ultimate damage load is between 8.0 kN and 8.6 kN, which is slightly lower than the initial one, because the filling area was destroyed. Both of the numerical and test results confirm that the filling area is the weakest part of the T-joints where the damage first appears. The crack then rapidly spreads to the glue film around the filling area. It was the peeling off of the glue film that accounts mostly for the failure of T-joints.