A　candidate　codec　for　ITU-T　Embedded　Variable　Bit　Rates　(EV-VBR)　standardization　designed　by　Speech　and　Audio　Signal　Processing　Laboratory　(SASPL)　of　Beijing　University　of　Technology　is　improved　in　this　paper.　In　the　improved　codec,　the　second　sub-frame＇s　spectral　parameters　are　quantized　additionally　to　improve　the　overall　quantization　precision.　Depth-first　tree　search　algorithm　replaces　the　full　search　and　focus　search　in　searching　algebraic　codebook.　Transformation　coding　(TCX)　process　is　redesigned　and　applied　into　the　higher　three　layers　which　reduces　the　algorithm　complexity　dramatically.　The　objective　mean　opinion　score　(MOS)　test　results　show　that　the　improved　codec　achieves　comparable　speech　quality　as　G.718　recommendation　codec　in　most　test　items　and　has　a　lower　algorithm　delay.　©　2009　IEEE.