Abstract: The evaluation of ecological security and controlling of desertification are focus of domestic and overseas researchers.In the paper, with the Shiyanghe valley of Gansu as an example, indexes of ecological security were const ructed, the ecological security was evaluated, and countermeasures of controlling desertification were put forw ard.Result s show that the ecological security of Shiyanghe valley was at a moderate level, that of the north of valley was w orse, and the area of oasis, economic development, utilization of water resources were main factors affecting the valley ecologcial security, and the natural and human factors were primary drivers of valley ecological security and desert ification.This paper is aimed at providing some theorical basis and reference to other regions of Gansu in terms of ecological security and desertification combating.

Key words: Shiyang river, ecological security, desertification, controlling