Permanent or seasonal snow cover is widespread on the Tibetan Plateau. Seasonal snow cover, which is affected by global climate change, is dominant in the northwestern part of Sichuan Province, on the eastern edge of the Tibetan Plateau. The root system is sensitive to environmental change. The effects of seasonal snow accumulation and thawing on soil physicochemical properties and microorganisms change could influence the root system in alpine meadow. Understanding the environmental effect on the root system of alpine meadow is essential to better understand the response mechanisms of terrestrial ecosystems to global climate change. From November 2013 to August 2014, we conducted the field study on controlled snow cover gradients in an alpine meadow of northwestern Sichuan. Four snow cover gradients were established: natural snowpack (control), and snowpack manipulated to be 2-, 3-, and 4-folds that of control. The root growth dynamics of plant communities and their responses to snow cover gradients were continuously monitored using the Minirhizotron method. The effects of the snow cover gradients on soil temperature were also measured. The results showed that soil temperature decreased with increasing snowpack volume. The optimum root system growth was observed with the natural snowpack. The root growth period was lower in the doubled natural snowpack compared with other treatments at the beginning, but the final root growth of was faster than that of the control. Belowground root system growth was restricted in the tripled snowpack. Correlation analysis showed that the root growth was positively correlated with soil temperature. Our results indicate that the winter snowpack change directly impacts subsurface ice storage, which in turn affects hydrothermal regimes in the alpine meadow soil and thus root system growth. Belowground root systems may suffer damage when the melt water refreezes underground after infiltrating into the soil and undergoes subsequent freeze-thaw cycles. Overall, moderately increased snowfall is conducive to the growth of the belowground root system, but excessive snow inhibits the belowground root system. Therefore, change in winter snowpack could alter carbon distribution and the carbon cycle in alpine meadow ecosystem.