In this paper, we performed calculations to investigate the dielectric, piezoelectric properties, Bo effective charge (BEC), and spontaneous polarization of Sr2M2O7, the method used in our study was a well-known density functional theory based on first-principles. The optimized results were in good agreement with previous experiments and calculations, which indicates that our calculated method is reasonable. The research we have done suggested that greater piezoelectric components of Sr2Nb2O7 were e31 and e33, and the contributions were derived from the A1. By studying the Bo effective charge, it could be seen that the valence of ions changed, and the O of Sr2Nb2O7 were most obviously that caused by the covalent character of ions and the hybridization of O-2p and Nb-4d. The spontaneous polarization of Sr2Nb2O7 in the [001] direction is 25 μC/cm2, while for Sr2Ta2O7, there was no spontaneous polarization in the paraelectric state. Finally, the effect of pressure on the piezoelectric properties were also investigated, the polarization of Sr2Nb2O7 decreased linearly with the increase after pressure. All our preliminary results throw light on the nature of dielectric, piezoelectric properties, Bo effective charge, and spontaneous polarization of Sr2M2O7, it was helpful for experimental research, the development of new materials, and future applications.