Ultraviolet (UV) light has long been known to damage nucleic acids. In this work, a DNA origami radiometer has been developed for measuring UV exposure by monitoring the morphological evolution of DNA origami nanostructures. Unlike linear DNA strands that tend to be degraded into small segments upon UV exposure, the structural complexity and interstrand connectivity of DNA origami remarkably alter the pathway of UV-induced DNA damage. A general pathway of expansion, distortion, and final disintegration is observed for DNA origami regardless of their shape and size; however the deformation kinetics is positively correlated with the number of nicks in the nanostructure. This structural continuity-dependent deformation can be translated into a DNA-based radiometer for measuring UV dose in the environment.