A sinusoidal wave modulation-based large-scale power transformer low-frequency heating device is provided. The sinusoidal wave modulation-based large-scale power transformer low-frequency heating device includes a phase-shifting transformer, an alternating current-alternating current frequency conversion device and a heated transformer which are connected with one another sequentially; a port at one side of the heated transformer is short circuited; the alternating current-alternating current frequency conversion device comprises two three-phase bridge rectifiers which are in reverse parallel connection; and the alternating current-alternating current frequency conversion device further comprises a frequency converter sinusoidal wave control unit, an output signal acquisition module and a frequency conversion power source main loop, wherein the frequency converter sinusoidal wave control unit comprises a sinusoidal wave modulation unit, a feedback control module and a conduction angle triggering controller. According to the sinusoidal wave modulation-based large-scale power transformer low-frequency heating device of the utility model, the two three-phase bridge rectifiers are in reverse parallel connection, and a thyristor natural current commutation mode is adopted to realize frequency conversion. Thus, the sinusoidal wave modulation-based large-scale power transformer low-frequency heating device has the advantages of stable and reliable operation, no direct current link, simple main loop, and high frequency-conversion efficiency.