We conducted a study to investigate morphological indicators, chlorophyll, soluble sugar, ergine and ergonovine contents under different photoperiods (8, 12, 14 and 16 h·d^-1) and illumination intensities (1 500, 2 500 and 3 500 lux), to explore the optimum conditions for the growth of the symbiotic Achnatherum inebrians seedling and the accumulation of alkaloids. it was found that: (1) the plant height, chlorophyll and soluble sugar content of symbiotic A. inebrians seeding were increased with the prolonging of photoperiod, which were significantly （P<0.05） lower than that of other three treatments under 16 h·d^-1, but the root length, tiller amount per plant and biomass per plant were increased first and then decreaseds, which had a peak value under 14 h·d^-1. （2） The plant four morphological indicators, chlorophyll and soluble sugar content of symbiotic A. inebrians seedling were increased with the illumination intensity increased that had a peak value under 3 500 lux. (3) With the prolonging of treatment time, the content of ergine and ergonovine were increased in different photoperiods. The contents of ergine and ergonovine were significantly （P<0.05） higher than that of other treatments under 12 h·d^-1 and 2 500 lux, which had a peak value at 15 days. It can be seen that the appropriate light environment can significantly promote the growth of symbiont of Epichlo gansuensisAchnatherum inebrians seedling and the accumulation of alkaloids, and the most suitable condition for the accumulation of ergine and ergonovine were 12 h·d^-1 and 2 500 lux.