An audio encoding method and device and an audio decoding method and device are provided. The audio encoding method includes: obtaining a current frame of an audio signal, where the current frame includes a high frequency band signal and a low frequency band signal; obtaining a compatible layer encoding parameter of the current frame based on the high frequency band signal and the low frequency band signal; obtaining an enhancement layer encoding parameter of the current frame based on the high frequency band signal; and performing bitstream multiplexing on the compatible layer encoding parameter and the enhancement layer encoding parameter to obtain an encoded bitstream.