The ultraviolet-screening pigment scytonemin is bio-synthesized in some sheathed cyanobacteria, exhibiting important ecological and medicinal values. Scytonemin is recognized to be predominantly induced by ultraviolet (UV)-A/B, but UV radiation is often inhibitory for cyanobacterial biomass increase. Here, we found that short-term shock (within 1 h) of natural sunlight could trigger a persistent production of scytonemin in cell suspension culture of Nostoc flagelliforme for several days. We thus exposed the cultures to solar radiation with different time intervals and durations, and found that everyday 30-min solar irradiation was the most effective for achieving the scytonemin production with less growth inhibition. Besides, the technological potential could be advanced by supplementing NaHCO3 or tryptophan in the cultural medium. This work presents a good example of rationally utilizing environmental solar radiation for effectively producing UV-inducible biochemicals in cyanobacteria. Display omitted •Short-term solar irradiation can induce persistent biosynthesis of scytonemin•Efficient scytonemin production by 60 min solar irradiation of every two days•More effective production of scytonemin by everyday 30 min solar irradiation•Elevated scytonemin production by adding NaHCO3 or tryptophan in medium