In order to solve the non-linearity errors due to the parasitic capacitors and random mismatches of the capacitive DAC array in the high-resolution applications of SAR ADC, this paper proposed a low-complexity capacitor mismatch detection and calibration technique for a differential capacitive DAC in the SAR ADC. The capacitor mismatches were detected with comparator and capacitors in SAR ADC itself without extra analog circuit. The obtained mismatch values would be used to correct bit weight of the capacitors in the DAC. AMS simulation result showed that the ENOB of 16-bit SAR ADC with capacitor mismatch increased from 10.74 bit to 15.38 bit.