Abstract: Five treatments (25%-30%, 50%-55%, 75%-80%, 95%-100% of field moisture capacity and submergence) were installed to study the effects of soil moisture on growth and physiological characteristics of Astragalus sinicus. Growth and accumulation of the nutrients absorbed by A. sinicus were greatest at 75%-80% of field moisture capacity, which was the best fit to growth. Disease symptoms of water stress were shown by A. sinicus at 25%-30% of field moisture capacity and at submergence. Compared with the 75%-80% of field moisture capacity treatment, superoxide dismutase (SOD), peroxidase (POD), catlase (CAT) activities and malondialdehvde (MDA) contents in leaves of A. sinicus and the minimal fluorescence (Fo) all increased significantly, while the maximal fluorescence (Fm), variable fluorescence (Fv), light energy transformation efficiency of PSⅡ(Fv/ Fm) and activity potential of PSⅡ(Fv/Fo) declined significantly as did the yield and accumulation of nutrients absorbed. SOD, POD, and CAT activities, MDA content and chlorophyll fluorescence parameters did not change significantly in the three treatments (50%-55%, 75%-80% and 95%-100% of field moisture capacity) which therefore showed that A. sinicus could normally grow at 50%-100% of field moisture capacity.