Abstract: The salinity-alkalinity of Songnen grasslands in Northeast China is aggravated due to natural and other human activities.Therefore,the local livestock husbandry is significantly hindered by decline of grassland biomass and the disappearance of high-quality forage species,thus salinity-alkalinity soil needs to be improved for sustainable animal husbandry development.Considering the soil,climate and water resources,we selected artificial grassland,which was set up on saline-sodic soils and ameliorated by sandy soils,to investigate the effects of soil salinity-alkalinity on alfalfa (Medicago sativa L.) bio-characteristics.Three degrees of soil salinity-alkalinity (mild,moderate and severe) were detected by EM 38,and soil samples (1.0 m depth) were collected for measuring the soil background of the field in 2015; in addition,alfalfa samples were collected twice for revealing the dynamics of alfalfa characteristics from 2016 to 2017.The results showed that there were negative correlations between soil salinity-alkalinity degrees and the growth rate,biomass,ratio of dry/fresh,Na/K and SPAD.With increasing salinity-alkalinity degrees,the growth rate of first and second harvests declined from 1.70 to 0.40 cm·d^-1 and from 1.40 to 0.45 cm·d^-1,respectively; SPAD diminished from 62.2 to 52.8; the Na/K decreased from 1.49 to 0.78; the forage biomass (dry weight) reduced from 1.88 to 0.20 t·hm^-2; the ratio of fresh and dry weight decreased from 2.59 to 1.80; while,the stem/leaf ratio increased from 1.72 to 2.61.Finally,results of this study indicated that the alfalfa dry yield and quality could be impacted by soil salinity-alkalinity.This study would offer basic theory support of the utilizations of saline-sodic lands and the promotion of saline-alkali artificial grassland productivity.