In　WI　coding　scheme,　how　to　decompose　and　quantize　the　characteristic　waveforms　with　low　delay,　low　complexity　and　high　precision　have　always　been　a　hot　research　topic.　The　characteristic　waveform　decomposition　based　on　non-negative　matrix　factorization　is　proposed　in　this　paper.　This　CW　decomposition　method　doesn＇t　bring　any　additional　delay　to　WI　coder;　In　order　to　improve　decomposition　precision,　the　CW　is　firstly　classified　according　to　the　maximum　pitch　of　its　sub-frames　before　being　decomposed.　Besides,　band-partitioning　initialization　constraints　are　set　to　basis　vectors　before　NMF　is　carried　out,　and　this　has　made　the　CW　decomposition　precision　of　NMF-based　method　be　comparable　with　that　of　2　ranks　of　SVD;　In　order　to　reduce　the　computational　complexity　of　WI　coder,　the　CW　alignment　procedure　is　removed　in　our　NMF-WI　coder,　and　the　factorization　rank　of　NMF　is　set　to　16　as　a　trade-off　between　computational　complexity　and　decomposition　precision.　In　the　end,　the　low　dimensional　coding　matrix　is　quantized　by　splitting　matrix　quantization　scheme.　The　subjective　A/B　listening　tests　show　that　the　proposed　2　kb/s　NMF-WI　coder　can　give　smooth　speech　with　quality　close　to　2.4　kb/s　SVD-based　WI　coder.　Mean　Opinion　Score　test　results　indicate　that　the　performance　of　proposed　coder　is　a　little　worse　than　that　of　2.4　kbps　MELP　coder.