Changing precipitation patterns and increased global warming will continue in the foreseeable future. Although the individual effects of warming and precipitation on plants have been studied, the interactive effects of these factors on plant functional traits, especially on indices of sensitivity degree and their adaptive thresholds, have drawn little attention to date. Climate control chambers were used to stimulate the sensitivity and adaptability of functional traits in Stipa breviflora to the interactive effects of warming (control, +1.5, +2.0, +4.0, +6.0°C) and changing precipitation rates (-30%, -15%, control, +15%, +30%) based on the average monthly temperature and precipitation during the growing season (from June to August) from 1978 to 2007. Stipa breviflora is a dominant species of desert steppe in the arid regions of north central China. Warming and changing precipitation had significant interactive effects on functional traits (except aboveground biomass and leaf number) in S. breviflora. Biomass characteristics were more sensitive to these changes than morphological characteristics, and belowground biomass was the most sensitive characteristic. Total biomass adapted in various ways to different regimes of warming and changing precipitation. Specifically, total biomass decreased linearly with increased temperature when precipitation decreased by 30%. However, no significant relationship between biomass and temperature was observed when precipitation decreased by 15%. Nevertheless, biomass had a quadratic curve relationship with temperature when the optimal temperature was 23.2, 24.4, 26.8°C under precipitation levels of no change (control), and increases in precipitation of 15 and 30%, respectively. Additionally, the optimal temperature for total biomass increased with increasing precipitation. The results presented here suggest that the growth of S. breviflora may be positively affected by slightly decreased precipitation and increased temperature in the future.