Abstract: Leaf area index (LAI) is a primary parameter for the energy flows and matter cycles in ecosystems. Since the ecological system in the arid area is extremely fragile, studying the LAI has great theoretical and practical contributions to monitoring and estimating the changes of ecological environment in arid lands. In this paper, we use the Vegetation Indexes (including NDVI, SAVI, NDMI, NBR, NBR2, MSAVI and EVI)-LAI method to estimate the spatial distribution characteristics of LAI value in the Yanqi Basin, Xinjiang, China. The modeling data is comprised of LAI and Vegetation Indexes,which were acquired by field measurements by LAI-2000 and indoor processing work of Landsat OLI remotely sensed image respectively. Then the LAI distribution map was acquired by using validated SAVI-LAI model. The spatial distribution characteristics of LAI in the study area were analyzed. The results show that:(1) All vegetation indices have good relevance with LAI, and among them the logarithmic function model of SAVI and LAI has the highest goodness of fit (R²=0.82). The estimation accuracy of LAI is about 89%, R²=0.86,RMSE=0.23; (2) There are three relatively high value areas in the distribution map of LAI,Bosten Lake Wetland area, the reeds area in the Huangshuigou River in northwest part of Bosten Lake and Oasis area in northern part of Yanqi Basin, and the highest LAI value reaches about 3.85. The LAI has the lower values in the transitional zone between the mountains and the plain area, and the desert area in the south, due to relative low water content for vegetation; (3) The characteristics of the LAI's spatial distribution are:an annular distribution of LAI centered the Bosten lake as a center; The LAI values decreased gradually along with the increase of the distance to the Lake and river.

Key words: vegetation index, retrieval of LAI, Landsat OLI, Yanqi Basin