Based on MATLAB/SIMULINK, this paper introduced a method of the systematic design and behavioral simulation of the sigma-delta modulator. Through the method, firstly，a performance-optimized modulator structure can be found by defining the order, OSR and the bit number of the inserted quantizer , optimizing the NTF zeros and scaling the structure coefficients of the modulator. Then the non-ideal modulator was modeled and simulated based on SIMULINK through the analysis of the modulator non-ideality, and the modulator sub-circuits performance was acquired finally. The simulation result of the modulator circuit designed under the guidance of the acquired sub-circuits performance shows that the acquired sub-circuits performance can guide the modulator circuit design effectively and reliably.