The invention relates to a resistance welding nugget quality control method, which comprises the following steps of: connecting a three-phase supply to a controller, rectifying through a current-limiting resistance rectifier diode and a full-wave half-controlled rectification circuit, filtering a capacitor through a control circuit, and converting alternating current into direct current; and inputting the direct current into an H bridge circuit consisting of insulated gate bipolar translators (IGBT), and outputting positive and negative half-wave alternating current from a UV end according toa main control circuit and a program. The key point is that: a welding parameter, namely a nugget coefficient c, is increased on the basis of an original welding parameter, and the current output waveform in each welding and heating period can be accurately controlled through two independent parameters, so that the welding current waveform control mode is radically changed, the regulation difficulty of the welding machine is reduced in the welding process, the depth of the nugget is increased, the splash is reduced, the sensitivity of a resistance welding machine to material change, power grid fluctuation and pressure change is reduced, and stable welding quality is easily obtained by adjusting the nugget coefficient c; moreover, the efficiency of the resistance welding machine is effectively improved.