Abstract: In view of the complex engineering & geological condition of a goaf during transition from open pit to underground mining，the orthogonal experiment is used for the design of the goaf and open pit′s backfilling scheme. Based on the stability analysis and economic comparisons of each backfilling scheme，the final backfilling scheme of goaf and open pit is given，and the impact of the backfilling on the third period project is pointed out. The research plays a guiding significance for the cementing filling of goaf under complex engineering geological conditions.

Key words: Cementing filling, Mixture ratio, Goaf, Open pit, Stability analysis