A digital foreground calibration technique, capacitor recombination technique, is proposed. The convergence speed of LMS algorithm was improved by combining this technique with LMS digital background calibration technique. The proposed algorithm was modeled using a 14-bit SAR ADC with RC hybrid structure. Simulation results show that the convergence speed of LMS algorithm can be improved to within 1 k conversion cycles, and the mean ENOB of the calibrated ADC is increased from 1059 bit to 1379 bit. The mean value of SFDR is increased from 7133 dB to 11293 dB, and the mean value of DNL maximum is increased from 188 LSB to 097 LSB. The mean value of INL maximum is increased from 801 LSB to 088 LSB.