An approach of speech inform ation hiding based on G．729 scheme，and ABS(Analysis—by—synthesis) algorithm of speech inform ation hiding and extracting， which form ing the theoretical basis for designing a secure speech com m unication system are proposed． A BS algorithm adopts speech synthesizer in speech coder，speech em bedding and coding are synchronous，i．e．a fusion of the inform ation data of secret and public speech． It can em — bed dynam ic data bits of secret speech into public speech， with perfect info rm ation stegan0grap hy and good speech quality． A BS algorithm is superior to available classical algorithm s in capacity and real-tim e．This approach is im — plemented to hide secret speech of 2．4kbps M ELP fM ixed excitation linear prediction)in public speech of 16kbps G ．729． Experim ents show that the approach satisfies the requirem ents of inform ation hiding，m eets the secure corn — m unication speech quality constraints，and achieves high hiding capacity of 800bps with an excellent speech quality and com plicating speakers’recognition．