A decoder system with double entry revolving transformer is designed based on the principle of double entry revolving transformer. The system converts revolving transformer input sine and cosine signals into a parallel natural binary digital word using the high accuracy analog digit conversion function of AD2S80A convert which is produced by the AD Company. And the parallel data from decoded AD2S80A is performed combination, calculation and error compensation using CPLD. The decoding principle of the double entry revolving transformer decoder system is introduced. The hardware combination and error compensation software flowchart are designed based on decoder principle to provide a feasible method to high accuracy decoder system of double entry revolving transformer.