A novel biological optimization algorithm, particle swarm optimization ( PSO) algorithm, is applied in defect identification in the paper. Diversified universal FEM software such as ANSYS or NASTRAN can be combined with the algorithm, since the hardwon calculation of gradient is not required, and the programming of FEM and op timization algorithm can be isolated effectively, which makesmany sophisticated cases solved easily. A simple defect identification case is also discussed in the paper.