Abstract: To study the relationship of external dump of opencast coal mine impacting on surrounding micrometeorological factors, and then provide the foundation acknowledge for the ecological restoration in mining area, the airflow movement and water distribution around the mine area were regarded as the influencing factors to furtherly explore the ecological effects of the scale and form of the external dump. Taking Hongshaquan open-pit coal mine as an example, using Fluent fluid simulation software, adopting large eddy simulation and component transfer model, the external dump models with different heights and angles were established for simulation. The monthly temperature and dew point data of the area in 2020 were obtained through the regional meteorological station where Hongshaquan open-pit coal mine located, thereby reaching the monthly condensation height of the area. By analyzing the cloud diagrams of air velocity and moisture mass fraction under different conditions, the influence law of different sizes of external dump on the surrounding air flow movement and water distribution was obtained, and compared with the condensation height in the area. The numerical simulation results showed that: with the increasing dump height, the air climbing speed increased slowly, while the maximum climbing height increased, as well as the moisture mass fraction on the windward slope and the dump top ascended. More and more obvious Karman vortex street phenomenon was formed along the leeward slope. The number of vortices increased and the influence range became larger. Both of the airflow velocity and moisture mass fraction in the vortex area increased and reached their maximum values. The increase in the angle of the external dump presented a significant impact on the maximum climb height of the airflow, but showed little impact on the surrounding micrometeorological factors. Under the condition of 360 m limit height, when the external dump Angle reached the critical value of 26°, the maximum airflow climbing height would reach the summer condensation height in this area. Alternatively, under the condition of 22° limit Angle of the outer dump, when the height of the outer dump reached the critical value of 380 m, the maximum climbing height of airflow would reach the summer condensation height of the region, thereby promoting the precipitation around the mining area