To investigate the response mechanism of biomass，photosynthetic and fluorescence characteristics of Glycyrrhiza seedlings to salt stress，the effects of salt stress on biomass and photosynthetic characteristics of Glycyrrhiza seedlings were studied with 5 NaCl concentrations of 0，50，100，150 and 200 mmol·L-1.The results showed that with the increase of salt concentration，the biomass of organs and total biomass of Glycyrrhiza inflata and Glycyrrhiza glabra decreased，reaching the lowest value in S4 and S3 treatments，respectively，while the ratio of root to shoot increased slightly.The SPAD value of Glycyrrhiza inflata was significantly inhibited by S2，which was 24.13% lower than that of S0，while salt stress had no significant effect on Glycyrrhiza glabra.Under salt stress (S1～S4)，net photosynthetic rate of two Glycyrrhiza inflata and Glycyrrhiza glabra seedlings decreased by 17.40%～66.86% and 14.62%～44.85%，respectively，compared with S0 treatment.Compared with S0 treatment，stomatal conductance decreased by 22.25%～81.81% and 34.62%～61.54%，respectively.Compared with S0 treatment，transpiration rate decreased by 29.97%～79.55 and 26.42%～53.45%，respectively，while intercellular CO₂ decreased first and then increased，and reached the lowest value in S2 and S3 treatment，respectively.The photosystem II activity，maximum potential light energy conversion efficiency，actual light energy conversion efficiency，electron transfer rate，photochemical quenching coefficient and non-photochemical quenching coefficient of two Glycyrrhiza seedlings decreased with the increasing salt concentration.Driving force analysis explained that the variation ratio of Glycyrrhiza biomass was 47.26%.In general，under salt stress，the decrease of net photosynthetic rate in leaves of Glycyrrhiza inflata was caused by stomatal restriction，while the leaf of Glycyrrhiza glabra was dominated by non-stomatal restriction.Glycyrrhiza glabra showed outstanding adaptability in growth and photosynthesis，and its salt tolerance was better than that of Glycyrrhiza inflata.