In the uneven electric field composed of corona pole and dust collecting pole, the  discharge electrode (corona pole) is  the cathode, the dust-collecting pole is anode, 72 kv high voltage power supply (high voltage silicon rectifier transformer rectifies 380 V alternating current to 72 kV high voltage direct current, high voltage electrostatic field is introduced by beam via the corona) occurs. When the electric field strength increases to a certain value, the  negative corna occurs around the corona pole , the  ionization effect  of gas molecule strengthens, producing a lot of positive and negative ions. Positive and negative ions are neutralized by the corona pole, the negative ions and free electrons shift to the dust-collecting pole. When gas with dust passes through, the particles with electric load will constantly encounter each other in motion and will be adsorbed on the dust particles, so the dusts are charged. Under the action of electric field force, the dusts move and arrive quickly on the dust- collecting pole (anode) ,to release negative charge and deposit on the dust -collection board itself. During running of the positive ions, the dusts in the corona zone are positively charged, and move to the corona board, so the dusts are accumulated on the corona, but the amount is less The dusts collected are vibrated by the rapping device and fall, and then they are gathered in the lower hopper to be conveyed by the ash-conveying motor, so the gas is purified.