The present invention discloses a fully digital Sigma-Delta modulator based on a phase inverter. The fully digital Sigma-Delta modulator comprises two integrators based on digital phase inverters which stabilize a working point under the effect of the auto-zero technology to realize feedback function in the integral process, a comparator based on a phase inverter which stabilizes a working point under the effect of the auto-zero technology to realize a high precision low power consumption voltage comparison function, and a feedback control logic formed by D latches and a gate circuit. The fully digital Sigma-Delta modulator can work normally under extremely low power supply voltage, the current utilization efficiency is high, and the power consumption is extremely low. A traditional amplifier is not used, however a digital module is used to carry out analog circuit design, the problems of small dynamic range, insufficient intrinsic gain, noise degradation and the like in the voltage design can be avoided, and the fully digital Sigma-Delta modulator is in accordance with the fully digital design trend of an analog-digital converter.