The invention discloses a high-precision correcting circuit for a band-gap reference voltage source. The circuit includes an operational amplifier, a capacitor, a PMOS tube and a trimming circuit. The opposite phase end of the operational amplifier is connected with reference voltage VBG generated by the band-gap reference voltage source, the in-phase end of the operational amplifier is connected with a first terminal Vf of the trimming circuit, and the output end of the operational amplifier is connected with a first terminal of the capacitor and a grid electrode of the PMOS tube; a source electrode of the PMOS tube is connected with an electric source VDD, a drain electrode of the PMOS tube is connected with a second terminal of the capacitor and a second terminal Vtop of the trimming circuit, a third terminal V1.2 of the trimming circuit is output voltage after correcting, and a fourth terminal Vbottom of the trimming circuit is connected with the ground. According to the high-precision correcting circuit for the band-gap reference voltage source, a snubber circuit in the band-gap reference voltage source is integrated with the correcting circuit, errors caused by influences of process corners, imbalance, temperature and other factors in the reference voltage can be corrected, the influences caused by fine adjustment on the temperature features of the reference voltage can be eliminated and the load carrying capacity of the output voltage is improved. By adopting a digital trimming mode, the high-precision correcting circuit has the advantages of being flexible in correcting, high in precision, low in power consumption and small in area.