Oxytropis ochrocephala Bunge is a poisonous legume plant which exhibits drought acclimation behavior and spreads rapidly under adverse environment. This study demonstrates that the stress signals including NO (nitric oxide), ABA (abscisic acid), and H2O2 (Hydrogen peroxide) are involved in roots of O. ochrocephala seedlings when exposed to drought stress simulated by PEG-6000 solution. The relationship among these signals was investigated by using exogenous and endogenous modulators. The results indicate that a time course of NO is accumulated in roots of O. ochrocephala in response to drought stress, which is generated enzymatically by nitrate reductase (NR) activity. The low level of NO acts as a downstream signaling of ABA and is involved with H2O2 signaling cascade. There is a regulatory mechanism of controlling NO concentration and maintaining the equilibrium state between ROS (reactive oxygen species) and NO, which modulates the root cell vitality, and osmotic adjustment thus improves root growth and developmental processes under drought stress.