A stress-corrosion cracking (SCC) test of TC4 titanium alloy in 3.5% NaCl solution was carried out, using modified wedge opening loading (WOL) specimens. The SCC behavior at various corrosion duration and loaded stress were investigated, and the mechanism of SCC was analyzed by microstructure and fracture morphology observation. The results show that, SCC propagation can be identified on the surface of specimen within 24 hours. The SCC lengths of specimens corroded for 30 days are similar with that of specimens corroded for 75 days. And both are significantly longer than that of specimens corroded for 15 days. This indicates that SCC propagation terminated within 15~30 days. SCC crack length increases with the enhancement of loading stress. Stress relaxation occurs along with crack extending, resulting in continuous reduction of residual K_I. When residual K_Ivalue decreases to about 38MPa.m_1/2^{, SCC propagation terminate}s. SCC behavior of the specimen could be attributed to coupling effect of stress and corrosion. Stress dominates the fast crack propagation at the initial stage of SCC, and the fracture surface presents dimple morphology. While the fracture surface exhibits cleavage morphology with scaly pattern at middle and later stages of SCC. And titanium oxide is found at the edge of scaly pattern. That is supposed to result from alternate repetition of crack residency after stress relaxation and crack continuous propagation assisted by anodic dissolution