The invention relates to a method for detecting the radiation energy attenuation rate of a UV curing light source, and belongs to the technical field of printing. The method comprises the steps: determining a band, which can represent the radiation energy attenuation degree of a band playing a role in curing, in a to-be-detected UV curing light source as detection light; preparing detection sheets V0 and Vm through neutral grey materials, preparing a light reduction sheet group and two light reduction sheets T0 and Tm through neutral grey materials, enabling a light source screening part, the detection sheets and the light reduction sheets to be stacked together and to be placed in a cylindrical device, and forming a detector which can observe a light transmission state visually; respectively using the detection sheets V0 and Vm and the light reduction sheets T0 and Tm in the detector at the moments when the UV light source is started and after use in some time, and determining whether the radiation energy attenuation of the light source reaches a value, which is m times higher than a designed value, or not through the judgment whether two light field parts reach a brightness difference or not. The method needs a simple device, and is suitable to be used in a production environment.