In　this　paper,　a　2kb/s　Waveform　Interpolation　speech　coder　is　proposed　based　on　non-negative　matrix　factorization　(NMF).　In　characteristic　waveforms　(CWs)　decomposition,　band-partitioning　initialization　constraints　were　set　to　basis　vectors　before　NMF　was　carried　out.　This　decomposition　method　only　requires　speech　signal　from　the　current　frame,　and　can　yield　high　decomposition　quality　with　low　computational　complexity.　Besides,　the　high　dimensional　CWs　matrix　can　be　expressed　by　the　low　dimensional　coding　matrix,　and　this　has　facilitated　the　CWs　quantization.　The　listening　test　shows　that　the　proposed　2kb/s　NMF-WI　coder　can　give　smooth　speech　with　quality　close　to　2.4kb/s　SVD-based　WI　coder.