The utility model relates to a three-phase rectifying power supply of an electric dust collector, comprising a high-voltage power voltage-regulating circuit, a high-voltage power voltage-regulating circuit controller and a variable voltage rectifying circuit; the rectifying power supply is characterized in that the high-voltage power voltage-regulating circuit consists of three paths of inverse parallel thyristor voltage-regulating circuits; the variable voltage rectifying circuit has a three-phase rectifying transformer; a secondary pole of the transformer is connected with a three-phase bridge type rectifying circuit; high-voltage alternating current is rectified to a path of direct current negative high voltage to output; in addition, the tail end of the three-phase bridge type rectifying circuit is connected with a sampling circuit which consists of a sampling resistor and a piezoresistor; and the signal input end of the sampling circuit is connected with a high-voltage power controller. The rectifying power supply has novel design and reasonable structure, and also has the following advantages that 1. the conversion rate of electrical energy is high and the consumption is little; 2. the average voltage of the output direct current is high, therefore, dust collection efficiency of ESP can be effectively improved; 3. the input power supply of the three-phase power is balance and the output voltage is smooth and stable; and 4. the energy-saving effect is good, therefore, the rectifying power supply is a high-voltage power of a novel dust collector with high efficiency, environment protection and being energy-saving.