Abstract: The mechanical behaviour of compositeπjoints under out-of-plane tensile load was investigated by the experimental and numerical simulation method. The tests were operated on the Instron 8803. During the experiments，the onset of the damage initiation，the failure process and their corresponding load were tested. The experimental results show that the fillers on the joint connection represent a potential zone of weakness and it is essential that their mechanical behaviour is well characterized. To simulate the mechanical behaviour of the weakness，basic assumptions and simulated method were presented. Based on the general FEM sof tware，the stress distribution of each composite lamina and filler was investigated with a 3D FE model and the estimated damage load was obtained by the modified maximum stress criteria. The filler as a critical component of the joint is pointed numerically，which is consistent with the experimental phenomena. At the same time，the predicted load of the onset of the damage has good agreement with the mean value of experimental data. These agreements verify the feasibility of the numerical analysis.