The present invention relates to a mouthpiece device of an electronic cigarette, including an atomizing device for vaporizing tobacco liquid into aerosol and a liquid reservoir for storing tobacco liquid in an inhaling shell. The device includes a plug-in rotary coupling for connecting the adaptor and attachment part in response to relative rotational movement about an axial direction. A clock switchover module is adapted to switch each of the first and second clock modules to change between the master mode and the slave mode.