Abstract: There were three continuous batch cultures, and by culturing in three photoperiod (i.e.,light∶dark ratio,respectively for 24 h∶0 h,12 h∶12 h and 8 h∶16 h),the effect of photoperiod on growth and activity of photosystem was studied in order to support artificial culture of Nostoc sphaeroides Kutzing indoor.The research results indicated that there was obvious growth inhibition of 24 hours continuous illumination on the second and third batch cultures,which indicate that 24 hours continuous illumination is not good for the long-term continuous batch culture of N. sphaeroides. The decline trend of Fv/Fm during the first batch culture indicate that photoinhibition existed in all the three treating groups, but it was quickly in the second and third batch culture. It was also proved that N.sphaeroides can reduce the photodamage to photosystem caused by longer duration of illumination by reducing the content of light-harvesting pigment in the antenna of photosystem, then higher photosyntheticefficiency can be obtained. N. sphaeroides does have regulation mechanism against photoinhibition, but the 24 h continuous illumination treating group showed irreversible inhibition of growth during the second and third batch culture.