The invention discloses an audio frequency bandwidth expansion method based on genetic algorithm optimized model parameters. The audio frequency bandwidth expansion method based on genetic algorithm optimized model parameters comprises following steps: 1, input audio frequency signal x(n) is subjected to pretreatment so as to obtain filtering signal; 2, the filtering signal is subjected to modulated lapped transform so as to obtain low frequency modulated lapped transform coefficient; 3, the low frequency modulated lapped transform coefficient is divided into sub-bands, the root-mean-square energy of each sub-band is calculated so as to obtain a low frequency spectrum envelope sequence; 4, based on the low frequency spectrum envelope sequence, gray model GM (1, 1) is adopted for estimationof high frequency sub-band energy of the audio frequency signal so as to obtain a high frequency spectrum envelope; 5, frequency spectrum coping, frequency spectrum folding, non-linear calculating, integration multi-band excitation or non-linear predicting method are adopted for audio frequency spectrum detail expansion so as to obtain high frequency spectrum details; 6 based on the high frequency spectrum envelope and high frequency spectrum details, recovery of high frequency spectrum information of the audio frequency signal x(n) is carried out; and 7, modulated lapped inverse transform isadopted to realize x(n) bandwidth expansion.