The invention provides an internal discharge process design method for period transition from metal strip mine mountain slope mining to deep concave mining, and relates to the technical field of stripmine mining. The internal discharge process design method includes the steps that step 1, during a transition period from metal mountain slope strip mine mining to deep concave mining, sectional mining advancement is adopted, and a stope forms different areas, namely, a first mining area and a post mining area; step 2, a development system is arranged on the final boundary of one side of the first mining area, after the first mining area leans on a wall, a fixed route is built, less temporary roads are built, and a fixed road which leans on the wall is adopted for transportation and dischargeof ore rock; step 3, trenching and excavating are carried out on the other side of the first mining area to build a temporary road, as the first mining area gradually leans on the wall and the bottomis exposed, an internal discharge route from the post mining area to the first mining area is planned one to two years in advance, and proper mining of the post mining area is carried out; and step 4, if a bottom pit of the first mining area is sufficient in space, an inner discharge area can be arranged in the first mining area, and enough safety distance is reserved in space between a mining area of the first mining area and the inner discharge area of the first mining area, the internal discharge can be started.