The invention discloses a data transmission method and system based on multi-frequency sound wave. The data transmission method comprises the following steps: calculating an error detection code and an error correction code of transmitted data, and adding the error detection code and the error correction code in the transmitted data; converting the transmitted data onto corresponding sound wave frequency to generate continuous audio information and play the continuous audio information, wherein each syllable of the audio information contains one or more frequency signals; when the audio information is received, analyzing the frequency signal from the audio information, and obtaining the transmitted data from the frequency signal. According to the data transmission method based on multi-frequency sound wave disclosed by the invention, the same syllable contains multiple kinds of frequency, so the encodable information of each syllable is increased and the code rate is improved, continuous errors are dispersed in an interlacing manner to improve the error correction ability and the anti-interference ability, two error detection modes and two error correction modes are used in a mixing manner to improve the error correction ability and the anti-interference ability, and synchronous alignment is carried out before decoding to improve the decoding success rate.