The invention discloses a system for purifying oil fume of a commercial kitchen and utilizing afterheat. The system comprises a flue, a mounting base, a horizontal pipe, an exhaust fan, a first flange, a bent pipe, a support base, a second flange, a multi-output high-voltage power supply, an oil fume purifying electrode, an electrode mounting pipe, an upper electrode mounting plate, a lower electrode mounting plate, an insulating pipe, an insulating material, a third flange, a first vertical pipe, a fourth flange, a second vertical pipe, an oil fume catalytic filtering unit, a fifth flange, a support rod, a pipe hoop, a flue outlet, a filter screen, a power supply, a heat exchanger, a heat-insulating layer, a cold water pipe and a hot water pipe. The system disclosed by the invention is capable of treating the oil fume of the commercial kitchen and then emitting into atmosphere, greatly increasing the emission efficiency, greatly reducing air pollution, utilizing the afterheat of the oil fume and meeting the requirement for hot water supply.