The present disclosure discloses an aerosol actuator and a metered dose inhaler. The aerosol actuator comprises a housing and a counting unit; the housing comprises a housing body and a nozzle, the housing body being configured to communicate with the nozzle; the housing body being configured to accommodate the counting unit; the counting unit comprises a gear fixing member, a counting gear, a driving element, and an elastic member; a cavity is formed inside the gear fixing member; the counting gear is arranged in the cavity; the gear fixing member comprises a cover plate part, the cover plate part comprising a cover plate part body and a check pawl; a surface of the counting gear that is close to the cover plate part body is provided with a limiting recess; the check pawl is arranged on the cover plate part body, and the check pawl is configured to coordinate with a meshing tooth of the counting gear so as to limit a rotation direction of the counting gear; the check pawl is provided with a limiting protrusion, the limiting protrusion being configured to coordinate with the limiting recess so as to limit a rotation direction of the counting gear. The aerosol actuator enables the counting to be more accurate.