Abstract: To study the effect of He-Ne laser radiation on differential thermal analysis(DTA) thermal parameters of folium isatidis exposed to ultraviolet B(UV-B) radiation,and further discuss the mechanism of laser biology,isatis indigotica seedlings exposed to UV-B radiation are treated with He-Ne laser.The experiments are divided into four groups,i.e.,comparison group,laser-treated group,UV-B treated group and UV-B and laser hybrid treated group.All DTA curves of the four groups represent one endothermic peak and two exothermic peaks and DTA parameters are different significantly among four treatments.The sequence of the total enthalpy value of the four treatments from the large to the small is laser-treated group,UV-B and laser hybrid treated group,comparison group,UV-B treated group,which shows that laser plays repair role on the seedlings lesion by UV-B damage.