The invention relates to the UV curing technology and discloses a UV lamp output power control method and a spraying and printing device based on the method. The UV lamp output power control method comprises the steps of controlling a UV lamp and switching the UV lamp among a plurality of operating stages by a controller; receiving UV rays emitted by the UV lamp at each operating stage by a UV detector to generate a UV detection signal corresponding to the above operating stage, and sending the UV detection signal to the controller; and according to a plurality of UV detection signals received by the controller and a preset power stored in the controller, setting a target operating stage of the UV lamp. When the spraying and printing device is in usage, the UV lamp is controlled by the controller to be switched at the target operating stage. At this time, the output power of the UV lamp at the target operating stage is just corresponding to the preset power. Therefore, the output power of the UV lamp is automatically detected and adjusted. The output power of the UV lamp is enabled to always meet the curing requirement.