Structural properties of AlxGa1-xN epilayers grown on (0 0 0 1) sapphire substrate by molecular beam epitaxy are investigated in the range of A1N molar fraction from 0.16 to 0.76. The A1N molar fraction estimated by X-ray diffraction agrees well with that of Rutherford backscattering spectroscopy, showing a good linear relationship. The uniform Auger electron spectroscopy depth profile and linear dependence of average atomic concentration of all the constituents of AlxGa1-xN epilayers on A1N molar fraction imply that the growth of AlxGa1-xN epilayers with variation of A1N molar fraction is well controlled without the compositional fluctuation in depth of the epilayer. It is observed by atomic force microscopy that the surface grain shape of AlxGa1-xN epilayer changes from roundish to a coalesced one with increasing A1N molar fraction.