The damage of the printed wring assembly (PWA) was treated as one of the main factors of the failure of electronic equipment. Thus the PWA must be studied and investigated. As the important prerequisite of the study, the dynamic characteristics of the PWA were determined in this paper. Here the dynamic characteristics of the PWA were modeled and analyzed by finite element analysis (FEA) method firstly, and then the experimental modal analysis (EMA) method was also used to study the dynamic characteristics of the PWA. The results obtained from above two methods were compared with each other, and good correlation was shown. So the correctness and accuracy of the FEA model was verified. On the base of that, the Z-axis (the normal of the board) of the PWA was determined as the main direction to be excited; subsequently the main modes in that direction were also determined. Furthermore the principle described as the components crossed by bend lines are detrimental to solder joint survival was used to prognosticate the packages which may be damaged.