An algorithm of locating the crack tip based on displacement filed around crack tip was proposed. Give the problem of locating the crack tip

the solution was tured to solving the minimum value by building the objective function including crack tip location firstly. And then the location of crack tips was assumed in a format of mesh

nonlinear optimal problem can be analyzed through a linear least squares approach after an assuming crack tip was chosen. The exact crack tip was gotten by iterative analysis. The results show that this algorithm has converged to the Ⅰ-mode and Ⅰ-Ⅱ mix-mode exact crack tip during four iterative steps in six seconds. The algorithm can provide technical assistance for crack measurement technique and has high engineering values.