The　recent　advances　of　large-scale　speech　corpus　(LSSC)　and　text-to-speech　(TTS)　technologies　are　briefly　reviewed,　then　the　architecture　and　annotation　information　of　a　large-scale　speech　corpus　Slib　are　introduced.　Based　on　Slib,　the　LSSC-oriented　indexing　methods　is　discussed,　the　set　operations　and　the　minimum　cover　problem　related　to　information　retrieval　in　LSSC　are　presented.　The　minimum　cover　problem　is　a　NP-complete　problem,　and　a　greedy　algorithm　is　proposed　to　obtain　an　approximation　solution.　The　approximation　ratio　of　the　proposed　algorithm　is　analyzed.　The　application　and　realization　of　set　operations　in　TTS　are　presented,　and　an　approach　for　choosing　proper　speech　instances　of　linguistic　units　based　on　minimum　cover　is　developed,　which　can　improve　the　naturalness　of　the　synthesized　speech　of　TTS　system.