By means of the theory of universal unfolding, the influence of multi_imperfections upon the critical load of structure in engineering is analysed in this paper.

In view of disadvantages in present defect reconstruction methods,such as over-long time or excessive need for training samples,a new defect reconstruction method based on similar model and genetic algorithm was investigated as follows:similar model between non-axisymetric defect and axisymetric defect was represented,and proportionality factor was deduced by skin depth equation.

The specific feature of the skin lamination defect on the moving steel strip surface is analyzed.