Considering recoil of electron, a new theory to explain axial channelling radiation is presented based on Compton scattering of virtual photon with relativistic electron. In the reference system of the electron at rest, the crystal field is taken as virtual photon. By Compton scattering of virtual photon with relativistic electron, the virtual photon can be transformed into real photon to radiate out. According to this theory, the precise wavelength formula of axial channelling radiation is obtained. The wavelength formula of classical theory is the approximate formula of the precise wavelength formula of axial channelling radiation. The precise power formula of axial channelling radiation is obtained. The results are consistent with classical scattering theory.