Abstract: Sigma-Delta modulators with accuracy above 14bit all adopt high order structure, which leads to high complexity problem. In this paper, a second-order 16 bit high-precision sigma delta modulator with switched capacitor circuit structure is designed by using the second-order structure and MATLAB SDtoolbox. The output results of the modulator are verified to have the accuracy of 16bit, thus reducing the order of the modulator above 14 bit. The effectiveness of the proposed method is verified by the simulation of a practical transistor level circuit.