The invention relates to a range hood and a work method thereof. The method comprises the following steps: during the cleaning procedures, a heating element (6) is connected, at least one fan system (2) is intermittently connected to dissipate the heat generated by the heating element (6), and the pressure generated by the fan system (2) is limited within a critical value so that an exhaust passage (4) of a range hood (1) can be closed by a gating element (5). Consequently, the range hood can be effectively and thoroughly cleaned or kept to be clean.