Abstract: The paper aims to know the process of drought disaster in desert ecosystem and the effect of drought on the growth of Agropyron cristatum and Cornulaca alaschanica and the release mechanism. The authors designed 3 kinds of treatments, which were drought stress, supplement irrigation and natural growth, and compared the changes of external morphology, yield and soil moisture index of the 2 herbaceous plants. Theresults showed that: the drought stress led to yellow withered stage in advance and the supplement irrigation made yellow withered stage delay; the drought stress delayed the flowering stage and shortened the reproductive period of Cornulaca alaschanica. Affected by drought stress, the growth height, dry matter, cover and soil water storage capacity of Agropyron cristatum and Cornulaca alaschanica decreased, and the effects of drought stress on the growth process gradually increased; 73 days and 88 days of turning green were start turning point of height growth of Cornulaca alaschanica and Agropyron cristatum, respectively. Affected by drought stress, 106- 121 days and 181- 197 days of turning green were the critical period of dry matter accumulation of Cornulaca alaschanica and Agropyron cristatum, respectively. Drought stress effect on soil water storage capacity was showed significantly from the flowering period of Cornulaca alaschanica, and had significant differences from the end of leaf expansion period of Agropyron cristatum, and with depth increasing, the decrease range of soil moisture storage capacity increased.