The invention discloses a low output ripple wave parallel power-factor correction (PFC) transform control method and device. The output end of a single-phase PFC convertor (TD) is connected in parallel with the output end of a DC (direct current)/DC convertor (DC-DC), and meanwhile energy is supplied to a load; the output positive end of the single-phase PFC convertor is mutually connected with the output positive end of the DC/DC convertor so as to form a 'Vo+' end, and meanwhile, the 'Vo+' end is connected with the positive end of the load; the output negative end of the single-phase PFC convertor is mutually connected with the output negative end of the DC/DC convertor so as to form a 'Vo-' end, and meanwhile, and the 'Vo-' end is connected with the negative end of the load; an input power supply of the DC/DC convertor is an auxiliary power supply; and an input source of the auxiliary power supply can generate the output of a rectifier circuit (REC), and the single-phase PFC convertor (TD) also can generate the output of the rectifier circuit (REC). The control method provided by the invention has the advantages of eliminating double line frequency output ripples of the traditional PFC convertor, meanwhile, improving the dynamic response of a system, and overcoming the problems that the traditional two-stage power-factor correction convertor is low in efficiency and high in cost.