The invention discloses an air conditioner indoor unit. The air conditioner indoor unit comprises a cover enclosure. A hollow accommodating space is formed in one end of the cover enclosure and is provided with an opening. A dust collection box device is arranged in the accommodating space. The dust collection box device comprises a support and a dust collection box detachably arranged on the support. The support moves up and down along the opening. The support moves downwards to drive the dust collection box to move downwards to extend out of the accommodating space to be exposed. When installed and dismantled, an operator just needs to push the dust collection box upwards or pull the dust collection box downwards along the accommodating space. The air conditioner indoor unit is convenient to install and dismantle. The operation process is simplified. The operation efficiency is improved.