Abstract: The waste dump of opencast coal mine is characterized by complex topography,loose stacking and strong heterogeneity. The long-term existence of the drainage field will produce some geological and environmental problems such as overall non-uniform settlement,slope instability deformation and peristalsis. Therefore,the understanding on the precise topographic data of the drainage field is the basis for ensuring its geological stability. However,the traditional topographic measurement technology is difficult to meet the requirement of high precision,and the terrain data obtained from low-altitude photogrammetry of UAV is influenced by surface vegetation,resulting in insufficient vertical accuracy. To overcome this problem,a method for obtaining topographic data based on the visible-light vegetation in- dex-vegetation height regression model is proposed. The surface elevation value obtained by UAV photogrammetry is modified using regression model to improve vertical high precision. Taking the north slope of the outer dump of the Baorixile opencast coal mine as the research object,the UAV photogrammetry technique was used to obtain the initial topographic and positive image data,and the vegetation index-vegetation height regression model was established to op- timize the initial elevation value. The results show that the visible vegetation index has a good correlation with the veg- etation height,and the estimation precision of vegetation index based on different bands has difference,and the vegeta- tion index EXG model (R2 = 0. 952) and RGBVI model (R2 = 0. 95) have high precision. Using the UAV Photogram- metry technique combined with the correction model to obtain the terrain data precision of the study area,the mean square root error of checkpoint is increased from 0. 111 m to 0. 045 m. Compared with the traditional GPS RTK terrain measurement technology,this method has a higher precision in the terrain complex,and obtains high-precision terrain data in medium and small scale.