By taking Ganzhou District in Gansu Province,a typical region in the arid inland river basin of Northwest China,as a study object and constructing comprehensive ecological security index and its assessment method,environmental impact assessments before and after land use planning were performed based on GIS techniques.Results showed that there was no extremely insecure area in the study region after performing land use planning.The ecological security index in the region was 2.453 on average,corresponding to a relatively secure statue.Result from the assessment may depict the spatial characteristics of environmental impacts by land use planning and can be used to identify the spatial variation and the problems influencing ecological environment,which implies that the comprehensive ecological security index and the evaluation method developed in the study are feasible basically.