The invention discloses a bandwidth expansion method of a stereo audio and an apparatus thereof. The method comprises the following steps of decomposing a stereo signal into a direct sound and a diffusion sound; according to a preset frequency band expansion method, carrying out bandwidth expansion on the diffusion sound; separating the direct sound into a plurality of point sound sources of different orientations, and carrying out bandwidth expansion on the plurality of point sound sources so as to acquire the plurality of point sound sources after the bandwidth expansion; remixing the plurality of point sound sources after the bandwidth expansion according to pre-estimated orientation information so as to the direct sound after the bandwidth expansion; according to the direct sound after the bandwidth expansion, combining the diffusion sound after the bandwidth expansion to reconstruct a broadband stereo audio signal. In the prior art, according to subjective quality of a single sound channel reconstruction signal, signal bandwidth expansion is realized, and correlation of signal energy and a phase in two sound channels is not considered so that a reconstructed stereo signal seriously influences determination of a listener to a sound source position and a distance. In the technical scheme of the invention, the above problem is solved.