Soil salinization has become a serious global problem, which poses a grave threat to ecological environment and agricultural production. In order to assess the effect of soil salinization on ecological environment quickly and accurately in regional-scale, a new remote sensing ecological index was proposed to detect the ecological change in arid area based on the remote sensing method in this paper. Manas river basin, a typical arid inland basin in northwest of China, was selected for the study area. Firstly, four indicators (salinity, surface albedo, vegetation coverage and wetness) which closely related to soil salinization were calculated based on the Landsat image in the Manas river basin on August 25, 1989, August 7, 2000, and September 10, 2015. Then, these indicators were normalized using min-max normalization method. Lastly, the principal component analysis (PCA) method was introduced to couple the four indicators, and the soil salinization ecology index (SSEI) was obtained. This method is different from the previous index overlaid by weighting the indexes from remote sensing and other data. It depends on the data itself, instead of subjective human states. The result shows that there is a significant relationship between SSEI and salt content observed in the fields (R²=0.9035, P < 0.01). This indicates SSEI could be used for retrieving the soil salinization on ecological environment rapidly and quantitatively. Through PCA analysis, we found that the first principal component appears stable and its share of all indicators is greater than 85%. The properties of wetness index (WI), normalized difference vegetation index (NDVI), and salinity index (SI) are consistent with the general ecological environmental parameters. The index was applied to the irrigated area of the Manas river basin. Among the bad, comparatively bad, medium, good, excellent grades, the area of bad grade had increased from 491.6 km² to 1031.4 km² during 1989 to 2000, but it has been decreased from 1031.4 km² to 636.9 km² during 2000 to 2015. The area of medium grade also increased at first but then reduced. The change area ranges from 6354.3 km² in 1989 to 2111.4 km² in 2015. The good and excellent grades of ecological environment has been increased by 12.9% in the last 26years, which shows the ecology environment has improved in the irrigation area. The spatial distribution of SSEI shows that the desert area without influencing by human activities still keeps a poor level, and the ecological problem is still very serious. The function of artificial oasis has been improving. Assessment of soil salinization ecological environment change using remote sensing technology could provide insight for land resource development in arid areas.