Appling one-dimension wave theory, the propagation of wave in composite sandwich plate and the local spalling fracture were studied. After the reflection and transmission of stress wave between different layers of sandwich plate were considered, theoretical formulae about the pressure time-history in different layers were got, calculation method for the promulgation of one dimension plane wave in sandwich plate was also founded. Based on the momentum theorem and the first strength theory, the theoretical formulae about the characteristics of movement and damage of sandwich plate were got. After comparing the results of theory and experimentation, the theoretical calculation method was proved. The analysis about defense characteristics of sandwich plate for blast loading showed that, the first steel plate and sandwich core can reduce the peak value of blast shock wave observably, but the second steel plate is the mostly part to resist blast shock wave, and the spalling of composite core also should be paid attentions to.