Abstract: To investigate the effects of precipitation pattern change on root morphological characteristics of Reaumuria soongorica seedlings in arid and semi-arid areas, a controlled experiment with two factors: precipitation [natural precipitation as control (W); W plus 30% (W+); W minus 30% (W-) and precipitation interval (5 days, T; 10 days, T+)], during the growing season. Results; (1): Root morphological indices showed an increasing trend with increasing precipitation with total root length, total root volume and root biomass increasing by 39.2%, 62.5% and 63.2%, respectively. (2): Extended precipitation time interval promoted seedling root indices with increased precipitation. When precipitation interval was 10 days and rainfall was increased 30%, the total root volume and root biomass were increased by 116.3% and 224.4% respectively (P<0.01). (3): Apart from specific root length and specific root area which were highest under natural precipitation and 10 day interval, remaining indices were not affected by the irrigation treatments. (4): Correlation analysis showed that the relationship between different indices differed under different precipitation patterns; total root length, total root surface area, total root volume, mean root diameter and root biomass were significantly positive correlated (r=0.5), indicating that R. soongorica seedling root systems possessed strong morphological plasticity. Both irrigation quantity and time interval significantly affected root morphology and there was an interaction between them, but the effect of rainfall was more important. R. soongorica seedlings showed strong morphological plasticity, being able to adapt to environmental stress by changing root morphological characteristics.