kb/s Finite State Algebraic Code Excited Linear Prediction （FS ACELP） is a high quality speech coding algorithm which has shorter time delay and low calculation burden.For line spectrum pairs

this algorithm uses a high efficient split vector quantizer based on intra frame and inter frame correlations.For adaptive codebook searching

it uses a finite state fractional delay adaptive codebook which has low calculation complexity and high performance.This algorithm also uses a state controled multimode algebraic codebook and a predictive vector quantizer for gains to further improve the quality of synthesized speech.The non formal tests show that the speech quality of 4kb/s FS ACELP is much better than that of IS 54 8kb/s VSELP and near to that of G.729 8kb/s CS ACELP while the MOS score is about 3.9.