The invention discloses a kitchen ventilator having an automatic washing function. The kitchen ventilator comprises a smoke collecting hood, wherein a smoke discharging channel is formed above the smoke collecting hood; the top of the smoke discharging channel is connected with an exhaust pipe to communicate with outside; a fan is mounted at a joint of the exhaust pipe and the smoke discharging channel; a water collecting tank is arranged at the bottom of the smoke discharging channel; washing liquid is accommodated in the water collecting tank; the inner part of the smoke discharging channelis divided into an inner pipe and an outer pipe in a sealing manner through a partition board I; the water collecting tank is arranged between the bottom of the inner pipe and the bottom of the outerpipe; the inner pipe is divided into a smoke sucking region, a fume separating region, a smoke gas filtering region and a smoke discharging region through partition boards III from bottom to top. According to the kitchen ventilator disclosed by the invention, fume is processed twice before discharging, so that the kitchen ventilator conforms to the environment-friendly requirements; besides, the washing liquid is used for continuously washing the inner part of the kitchen ventilator in a recycling manner, so that the phenomenon that the kitchen ventilator is disassembled for washing is avoided, and the smoke discharging pipeline is kept clean for a long term.