The response of root length, plant height and basal diameter growth of dominant plant species in Mu Us sandland to atmospheric CO_2 enrichment and soil drought is experimental studied. The results show that the impacts of atmospheric CO_2 enrichment and soil drought on plant growth are complicated. The response of different plant species to CO_2 is different, but the response of different plant species to soil drought is different too. Therefore, the compound impacts of atmospheric CO_2 enrichment and soil drought on plant are very complicated.