Abstract: In order to study the effect of exogenous selenium on chlorophyll fluorescence characteristic of foxtail millet, a field experiment was conducted with ‘Changnong35’ by the method of randomized block design. Through foliar spray of different concentrations of sodium selenite in millet heading stage, the variation trend of chlorophyll content, leaf SPAD value and chlorophyll fluorescence parameters were analyzed. The results showed that exogenous selenium could significantly improve leaf chlorophyll content and change chlorophyll fluorescence characteristic, the optimum amount of selenium could improve the maximal photochemistry efficiency (Fv/Fm), which could also increase electron transfer (ETR and Ф_PSⅡ) and photochemical quenching coefficient (qP), and reduce the non-photochemical quenching coefficient (qN), thereby reduced the heat dissipation of PSⅡ light energy and increased the photochemical efficiency of PSⅡ. Foliar spray of selenium on foxtail millet had obviously positive effect on leaf chlorophyll content, leaf SPAD value and chlorophyll fluorescence parameters, the optimum spraying concentration was 67.84 g/hm² in heading stage, which could obtain the best effect.