In order to realize analog-to-digital conversion with low distortion and high dynamic range, a new high-precision Sigma Delta modulator system is proposed. The Sigma-Delta modulator firstly adopts a new type of second-order single-loop one-bit quantization structure, where adds two feedforward paths and adjusts the logical relationship between the core integrator and the adder module. At the same time, in order to realize the second-order shaping of quantization noise and the delay-free transmission of input signals, the transmission function of the integrator is further adapted and improved. Matlab based system-level simulation results show that, the signal-to-noise ratio (SNR) of the proposed modulator is 106.6dB, the effective number of bit (ENOB) is 17.41bit, the second harmonic distortion is -82.7dB and the dynamic range is 104.76dB under the conditions of sampling signal frequency of 1024KHz and input signal bandwidth of 1KHz, which provides a new direction for the research and development of Sigma-Delta modulator with high-order MASH structure.