Abstract: How to determine the ecological impact boundary of coal mining is one of the difficulties in the research field of land ecology in mining areas. For a long time, surface subsidence depth of 10 mm is generally used as the coal mining disturbance boundary not only to the developed land but also to the vegetation-covered land in the academic research and planning practice. Land reclamation is still bounded by the subsidence contour with the expected surface subsidence depth of 10 mm as the boundary. In fact, many scholars and other professionals have realized that 10 mm sinking is not adaptable as the boundary of mining influence on land ecology. Our research goal was to find a remote sensing method to identify mining impact boundary, which could be used to evaluate ecological accumulating effect of coal mining on vegetated area. Yanzhou coal field, a typical coal mine area with high groundwater level in the eastern China, was taken as the study area, where the coal mining has caused a lot of impounded water areas, and the spatial distribution characteristics of the temperature vegetation drought index (TVDI), which is linear with soil moisture, were analyzed. Then the influence boundary of mining subsidence on soil moisture was determined, and the difference between the influence boundary using TVDI spatial changing tendency and the expected surface subsidence of 10 mm was analyzed. Firstly, the authors calculated TVDI and found it was mainly concentrated in the range of 0.2-0.6, which meant soil moisture levels were mainly “normal” and “slight drought”. The areas belonging to “normal” level and “slight drought” accounted for 45.17% and 40.09% of the whole study area respectively. Secondly, the authors tried to obtain the influence boundary of soil moisture and analyzed the spatial distribution characteristics of TVDI from the edge of the impounded water area by mining subsidence. The impounded water areas i.e. A, B, C, D, F, G and H were taken as the research objects and the different distance ranges from the edge of the impounded water area were divided. With the increase of the distance from the edge of the impounded water area, the median TVDI value increased and then tended to be stable. Due to the differences in coal seam, mining methods and processes, the influence range of coal mining on soil moisture varied in different subsided areas. The authors proposed an exponential model to identify the mining influence boundary, in which the value of asymptotic line was defined as the disturbed boundary. Study results showed that TVDI stable value in each impounded water area is between 0.38 and 0.43. Fitting TVDI value with exponential function, it could be found that the correlation coefficients are greater than 0.60, and the mean square root errors are less than 0.02. The impounded water area H is fragmented, irregular and has strong internal spatial interaction, which has the largest influence distance reaching 781 m. Finally, the ecological disturbance range of coal mining based on TVDI extraction method was expected to be smaller than subsidence depth boundary, namely 10 mm. The paper?s innovation is to propose a new method to identify the mining influence boundary, which is the theoretical boundary is the asymptotic line of ecological index changing from the edge of impounded water area to the unmined area by increased disturbance range.