Abstract: With the development of high density and high integration packaging technology, the reliability of packaging structure has attracted much attention. In this paper, a compact and high sensitivity 3D optical testing method is constructed by effective combination of Moiré interferometry with Twyman/Green interferometry and by implementing phase shifting technique. In order to further improve the stain accuracy, the discrete deformation field obtained by the phase shifting technology is fitted with polynomial, and then the derivation is realized. The measurement accuracy of the method is verified by the three-point bending experiment of the standard test piece, and the deformation of the typical Ball Grid Array(BGA) package structure under thermal load is finally measured. The deformation and strain information of package structure under thermal and force loads can be obtained by the method, which is of great significance to improve the reliability of package structure.