Abstract: In order to clarify the effect of mixed saline-alkali stress on the germination of Platycodon grandiflorum seeds, the methods of improving the germination of Platycodon grandiflorum seeds under saline-alkali stress were studied.The seeds of Platycodon grandiflorum were used as research materials, the effects of mixed saline-alkali stress on seed germination of Platycodon grandiflorum were studied by mixing neutral salt（NaCl, Na₂SO₄） and alkaline salt（NaHCO₃, Na₂CO₃） in different proportions to cross-simulate 20 different mixed saline-alkali combinations, to explore the effects of different concentrations of spermine on seed germination indexes under screened mixed saline-alkali concentration combination C（1∶9∶9∶1） stress whose inhibition effect was the most significatant. The results showed that the seed germination rate（Gr）, germination potential（Gv）, germination index（Gi）, vigor index（Ai） and relative damage rate of Platycodon grandiflorum were affected by mixed saline-alkali stress to different degrees, and the correlation analysis showed that the salt-alkali concentration was the main factor to inhibit the germination of Platycodon grandiflorum seeds.The germination of Platycodon grandiflorum seeds was promoted by low concentration of spermidine and inhibited by high concentration of spermidine. The optimum concentration of spermidine was 0.5 mmol/L.This study could provide a theoretical basis for the selection of saline-alkali land and the improvement of salt tolerance of Platycodon grandiflorum seeds in the process of standardized planting.