The invention provides a locking device of a smoke barrier at an air inlet of a range hood. The locking device comprises a driving device and a buckle, wherein the driving device is arranged at inside of a panel of the range hood; the buckle is positioned at the lower end of the smoke barrier which is hinged on the air inlet of the panel; and the locking device is characterized in that a fixing member is connected to the lower part of the driving device; and the driving device drives the fixing member to move so that the fixing member is buckled with the buckle or loosened so as to lock or open the smoke barrier. The locking device of the smoke barrier at the air inlet of the range hood is simple in structure and convenient to produce and assemble; and through the locking device, the automatic locking and open operation of the smoke barrier can be realized; the oil fume backflow caused by untight closing of the smoke barrier can be prevented; the environment of a kitchen is cleaned; the situation that the locking device cannot be used caused by oil pollution can be avoided; and the service life of the locking device and the service life of the range hood are guaranteed.