The present invention relates to an audio data retractile encoding and decoding system and method. The audio data retractile encoding method includes additional information in accordance with scaling factor information and encoding module information of the first layer; plural quantized samples are encoded by the unit of a symbol according to a sequence from a symbol with an MSB (Most SignificantBit) to a symbol with an LSB (Least Significant Bit) referring to the encoding moduel information. According to the invention, fine granularity scalability, lower complexity and good audio quality are provided according to the present method, even in a low layer.