The invention provides a mobile air conditioner. The mobile air conditioner comprises an upper layer water receiving tray and a chassis structure. The chassis structure comprises a water absorption zone, a water tank zone, a water pumping zone and a water level control zone. The chassis structure further comprises a water retaining rib for isolating the water absorption zone from the water tank zone, and a convergence part which is located between the water pumping zone and the water tank zone and is close to a convergence port of the water pumping zone, wherein a water pumping wheel is arranged on the convergence part; and at least one support rib is arranged in the water tank zone. According to the mobile air conditioner, cooperation of the upper layer water receiving tray and a chassisis utilized, water on the upper layer water receiving tray and the chassis in the mobile air conditioner can be reasonably distributed, the water pumping zone is preferentially supplied, water on theupper layer can be directly supplied to the water pumping zone, the water cycle steps are reduced, and the water pumping efficiency is improved.