Abstract: The region of Brahmaputra River and its two tributaries is one of the important typical agricultural area in Tibet Plateau.The development of agriculture depends on natural environment strongly which makes the cultivated land area is narrow.The arable land is only distributed in valley and its restrictive factors are prominent.To identify and measure the influence factors of cultivated land distribution has a realistic significance for the agricultural development and cultivated land reconstruction.According to this, the paper used the existing data in the region of Brahmaputra River and its two tributaries to analyze the regularity distribution and its reclamation strength in different altitude and geomorphic unit.We found that the proportion of grids whose reclamation ratio was 10%-30% was the biggest and it accounted for 29.39% of total grids with cultivated land.The cultivated land was mainly distributed on the diluvial plain in wide river valley with the altitude of 3700-4100 m.The proportion of its arable land was up to 59.85%.Partial least squares regression (PLS) is a method of multivariate statistical data analysis with the characteristics of multiple linear regression analysis, canonical correlation analysis and principal component analysis method.To explore the relationship between cultivated land and natural, social and economic influencing factors, we took the proportion of cultivated land in each 1 km × 1 km grid as the dependent variable, and 12 impacting factors of cultivated land as the independent variable, which consisted of elevation, slope, aspect, precipitation, accumulated temperature of higher than 0 ℃, average July temperature, average January temperature, solar radiation, soil organic matter content, soil thickness, distance from the nearest town and distance from the nearest river, and established the PLS regression model, using the variable projection importance index to measure the interpretation capacity of various factors on the variable.The results showed that the influence of 12 factors on the intensity of cultivated land reclamation was slope > solar radiation > average July temperature > elevation > precipitation > distance from the nearest river > average January temperature > distance from the nearest town > accumulated temperature of higher than 0 ℃ > soil organic matter content > soil thickness > aspect.The variable projection importance index value of slope was 2.2269, and slope had the strongest explanation and was the most important influencing factor to the land distribution.It concerned the difficulty level of land reclamation; the more flat the area, the easier to reclaim.Heat condition of cultivated land distribution also had an important influence.The values of average July and January temperature were 1.0967 and 0.8187, respectively, and both of them had strong explanation to cultivated land.The elevation was also important with the value of 1.0954.Altitude limited the distribution of cropland, and by influencing the heat change in vertical direction, it influenced the distribution of cultivated land.Because of the river valley landform, accessibility factors included distance from the nearest town and river were ranked in front in the influencing factors, and their values were respectively 0.7588 and 0.8442, respectively.The influence of soil factors on the cultivated land distribution was not obvious.It reflected that the distribution of cultivated land was mainly controlled by topography and climate.