The so-called arid regions of China in this paper do not include the semiarid regions and only refer to such lands as Xinjiang, the Hexi corridor of Gansu, the Qaidam basin of Qin-ghai, northern Ningxia, western Inner Mongolia, etc.The runoff in China's arid regions shows horizontal zonality and vertical zonality, the latter being more obvious. The lofty mountain masses, such as Altai, Tianshan, Qilian, Kun-lun, Altun, Helan, ect., are capable of intercepting moist air currents to produce mere precipitation than that occurring on the surrounding plains. Therefore, from the viewpoint of runoff situation, the arid regions can clearly be divided into the belts of the runoff formation and those of the runoff disappearance. The runoff formation belts and the runoff disappearance belts in arid regions have fundamental difference in hydrological regime.The hydrological regime of the river and its evolution depend mainly upon the supply sources of the runoff. The diversity of the runoff supply sources is one of the hydrological cha-racteristilies in the arid regions. The melt water from the alpine ice and snow has great impact on the hydrological regime of the river.The groud water of the piedmont plain comes mainly from surface water, while the river water below the plain comes partly from ground water. Between the river water and the ground water exists a relation of mutual supply, i.e., mutual transformation.