The invention relates to an ultraviolet single-effect falling film type disinfection apparatus, which comprises a liquid inlet, a nozzle, a disperse segment, a distribution plate, an ultraviolet lamp pipe, a gap adjustable ring, a adjustable ring control handle, a pipe pallet, a liquid outlet and a steam pipeline; the liquid inlet is positioned at the top of the disinfection apparatus and is connected to the nozzle, then is passed through the disperse segment and is connected to the distribution disc, the grooves with caliber slightly larger than the external diameter of the ultraviolet lamp pipe are uniformly distributed on the distribution plate, the gap adjustable ring is arranged at the lower part of the groove, the gap adjustable ring is connected to the control handle arranged outside the disinfection apparatus, the ultraviolet lamp pipe is passed through the groove and is placed with the gap adjustable ring on the pipe pallet wt the lower part of the disinfection apparatus, the liquid outlet is arranged at the lower part of the pipe pallet, the steam pipeline is communicated to the liquid outlet, and forms an angle of 90 DEG with the liquid outlet. By employing a film distribution technology, the liquid material thickness can be controlled, disadvantage of insufficient penetration capability of the ultraviolet ray can be reduced, ultraviolet irradiation time is greatly shortened, and the ultraviolet lamp pipe capable of emitting two types of wavelength can be ingeniously matched, so that bacteria in the beverage can be effectively killed.