The automatization of crack expand simulation is carried out by the programmer, using the simulation technique of singular unit, base on the ANSYS software. The nodes are dispersed by crack front. The singular unit is using to radiate from the nodes. The restriction is used at the edge of model. The stress intensity factor is worked out. The expansion ratio is confirmed. Then the displacement of crack expansion of the nodes is resolved. The way of expansion of crack front is orthogonal. The semi-ellipse curve of crack expand is worked out by numeric analysis. The simulation of crack expansion is carried out. The system of MTS（Material test system）810 from USA is used. And the experiment of crack expand is carried out with the load of tension. On the other side, the new crack front is fitted to get continual extension simulation.