The influences of blue light on the inactivation of pathogenic microorganisms with catechin photoreaction were discussed in this study. Blue light could be thought a new light origin for catechin photolysis. Chromatographic assay showed that the yellowish catechin dimer was produced from the electron transfer of catechin photolysis in an alkaline solution condition. Catechin upon addition of ascorbic acid or gallic acid can suppress the photolysis for ROS formation and inhibit the catechin photolysis. The catechin photolysis with blue light was able to inactivate Acinetobacter baumannii, including a carbapenem-resistant strain by ROS formation. Catechin photochemistry might be a safe and simple technique for hygienic decontamination.