Critical damage value of material was obtained by physical experiment combined with a finite element software. True stress-strain curve of Ti600 alloy was studied by high temperature tensile test at 1010℃ and 0.001s^-1. A simplified Normalized Cockcroft & Latham ductile fracture criterion was used, in which ε and σ were substituted by ε₁ and σ_UTS, respectively. The critical damage value of Ti600 alloy on the above experimental condition was calculated and then was embedded in a finite element software to verify its accuracy by analysing high temperature tensile process. The result shows that the critical damage value of Ti600 alloy at 1010℃ and 0.001s^-1 equals 0.643. By the finite element analysis, the crack initiation and propagation are predicted well and computational variety law of minimum cross sectional area is basically agreed with the experimental law. Hence, the critical damage value of Ti600 alloy obtained by combining a Normalized Cockcroft & Latham ductile fracture criterion with a finite element software is fairly precise.