Grinding forces during grinding silicon wafer have great influences on the accuracy, surface quality and grinding yield of the wafer. It is necessary to develop an accurate and reliable grinding dynamometer for measuring and monitoring the grinding process of the large and thin wafer. In this work, a new 3D (three-dimensional) grinding dynamometer using piezoelectric sensors is designed and developed, which is used for a wafer grinder based on wafer rotating grinding method. The calibrating experiments of the 3D grinding dynamometer are carried out. The FEA and modal analysis are made and compared with the results of mode testing. Furthermore, the static performance parameters of the dynamometer are obtained from the loading experiment. The experiment results indicate that the 3D grinding dynamometer can measure axial, radial and tangential grinding force of grinding wheel with high sensitivity, good linearity, good repeatability and high natural frequency, and fully satisfied requirement for measuring and monitoring of the grinding force in wafer grinding process.