In connection with the diversity of the IED input analogs in digital substation resulting in synchronization with different sampled values and different sample frequencies， an analysis is made of the time sequence of the IED sample in a digital substation and the factors for consideration in the synchronization and interpolation algorithm of sampled values from the perspective of IED data processing. Then the design of the synchronization and interpolation algorithm of sampled values is described. The method proposed has improved the effectiveness of the whole sampled values in different sampling modes.