Abstract: Under enhanced UV-B radiation,the effect of He-Ne laser(5.23 mW/mm²,5 min/d) radiation on component,content of the flavonoids and growth parameters in Beta vulgaris var.cicila L.were studied.The content of methanol-soluble flavonoids in leaves were determined by using the method of high performance liquid chromatography (HPLC).The results showed that the total falvonoids content treated by UV-B radiation(B) were increased to 160% compared with that of control(CK,no UV-B radiation),while it was only slightly higher in laser and UV-B combined treatment group(BL).There was no quercetin in leaves of CK,while it was induced substantively by He-Ne laser(L),UV-B radiation and their combined treatment.Meanwhile,flavone could be found only in leaves of CK and L group.The results suggested that the induction of UV-B absorb substance by He-Ne laser is selective,which is similar to that of UV-B radiation.Thus,it is very likely that this selective mechanism is the way by which the He-Ne laser treatment alleviated the damage of UV-B radiation.