Abstract: Analytical study on the surface crack propagation of gas cylinder by Franc 3D numerical simulation method and submodeling technique was conducted.The dynamic numerical simulation and three dimensional stress intensity factor calculation were conducted to prove the validity of the method and the iteration formula method was also used to verify the accuracy of this method.Based on the calculation results and in consideration of safety magin, we estimated the remaining life time of two cracks with initial dimensions of a₀= 3 mm, c₀= 6 mm and a₀= 3 mm, c₀= 9 mm were 3.5 a and 2.6 a respectively.