Sigma delta modulator design automation from system to circuit is presented in this paper. The sigma delta modulator design flow is separated into the system and circuit level design. It often adopts Matlab Simulink for the system level design and utilizes circuit simulator Spectre for the circuit level design. We propose a methodology which is realized by a script language PERL to control and link all these simulation tools. For the purpose of the automation, we also applied simulated annealing algorithm to optimize the system parameters in the script. We have successfully implemented this automation flow for the switched-cap third-order feedback single loop single bit with the simulated annealing algorithm. The designer of the SDM is complete within one day and shows the SNDR up to 87 dB. Besides, this methodology can be applied to any architecture of the sigma delta modulators only if the system is modeled well in the behavior model.