The invention discloses a paste filling method for end slope of an opencut coal mine. The paste filling method comprises the following steps: according to excavation situations and occurrence characteristics of a coal seam of the opencut coal mine; slicing by using an end slope coal mining system; meanwhile, finishing the arrangement of a past filling station on the ground; preparing a filling material; mounting filling matched equipment; laying a filling pipeline; after end slop coal mining is ended, filling by adopting a paste filling technology in time; solidifying a filling body to have a certain strength and enabling the solidified filling body to serve as a side slope and a false roof for subsequent slicing. The mining and filling are performed in different roadways, thus mutual influence is avoided; main materials for filling the paste are sourced from peeled slag stones in main accesses of a mining area, so that the problems of land occupation, environment and the like due to waste stone discharge are effectively solved, and the advantages of reducing surface subsidence, protecting ground surface buildings and vegetation and the like by the paste filling method are fully played. According to the method, the governance of mining situations of the mining area, resource development and environmental protection are integrated, and the damage to the ecological environment of the mining area due to mining is remarkably reduced.