In order to meet the requirements of high-precision current feedback in power control and real-time current detection in fault monitoring of grid-connected inverters, a new method of grid-connected inverter current acquisition and rapid overcurrent detection based on Sigma-Delta ADC technology was proposed. In this method, two SinC3 filters with different extraction rates were used to demodulate the filtered data stream respectively, which achieved the flexible usage of the modulation on the same data flow. The data stream was modulated by a second order sigma delta modulator,SinC3 filters were implemented in the digital signal processor (DSP). Test results show that the proposed method realizes the inverter grid current 13 effective resolution bit isolation sampling and 3.4μs rapid over-current detection.