A high-efficient one-step mining method, Non-pillar continuous mining (NPCM), was originally put forward and carried out in a copper mine in Anhui Province, southeast of China. Reliability theory was employed to analyze the stability of the critical structures, including temporary ore wall and backfilling in substope of NPCM, which was completely different from the traditional analysis method, the deterministic value analysis method. Anti-overturning and strength limit state equations for temporary ore wall in NPCM were derived, and reliability index (β) and safety factor were calculated. The relationship between the reliability index and width of the temporary ore wall were shown. Further, this paper established a 3-D limit state equation of back-filling in sub-stope of NPCM. Using the 3-D limit state equation the safety factor of backfilling in substop and its reliability index were obtained.