UV irradiation at 10 J/m 2/min induced a mild toxicity on locomotion behaviors and stress response in Caenorhabditis elegans. Pre-treatment with UV irradiation at 10 J/m 2/min at L2-larva stage prevented the formation of locomotion behavioral defects, and activated a noticeable reduction of stress response and oxidative damage in 50 and 100 μM metal (Hg, Pb, and Cr) exposed nematodes. Pre-treatment with UV irradiation at 20 J/m 2/min caused a significant decrease of locomotion behaviors in metal exposed nematodes, and pre-treatment with mild UV irradiation could not prevent the formation of locomotion behavioral defects in 200 μM metal exposed nematodes. Moreover, the adaptive response to toxicity on locomotion behaviors induced by metal exposure was not formed in mev-1 mutants. Therefore, pre-treatment to mild UV irradiation activates the cross-adaptation response to toxicity on locomotion behaviors induced by metal exposure, and this kind of adaptive response may be under the control of MEV-1 function.