Abstract: The 6143 working face is the first and longest mechanized mining face with a large mining height in large dip seam of Huashan Coal Mine. In order to ensure safe and quick installation, the horizontal lowering quick installation technology of the support is adopted in the open-off cut by making full use of the support sliding in the large dip open-off cut, and large space has been obtained by means of bolt-mesh-anchor support without stand column for the open-off cut. The key of this technology is to use the main and auxiliary winches to pull the supports down horizontally, and the slippery unloading, which eliminates the defect of the traditional vertical lowering installation of the support which needs to be first turned and then anti-turned by 90°. This ensures the safety of the operators on the large dip slope and improves the support installation efficiency.