The invention is concerned with the correcting convertor of the single power factor circuit. The positive output end of the rectifier of the transformer meets the tip of the primary winding of the transformer, the bottom of the primary winding of the transformer meets the negative output end of the rectifier with the switch in the middle, the cathode of the first diode meets the positive end of the rectifier, the anode of the first diode meets the negative end of the rectifier with the circuit in series in the middle, which composes by the second diode and the second winding of the transformer, the storing capacitance anode meets the connecting point that is in the middle of the series circuit and the first diode anode, the storing capacitance cathode meets the negative end of the rectifier. The invention can eliminate the surge current generated by the power during starting up, can reduce the voltage of the storing capacitance to less than 250V, and it can recycle the magnet leakage energy of the transformer to improves power efficiency. It suits for the switch power in middle or small power.