Abstract: With regard to the Titanium alloy welding structures generally used in advanced aircraft structures,an equivalent theoretical stress concentration coefficient Kt (K_te) was introduced to describe the fatigue property of welding specimen. On the basis of the fatigue properties of Titanium alloy specimens,a technological approach used to determine K_te is established through fatigue testing for the Titanium alloy welding specimen under a spectrum load. The detailed process determining K_te and some useful results are given by taking the TC4 titanium alloy oxy-arc welding specimen for example.