The distribution of Sb atoms in δ-doped silicon crystals grown by molecular beam epitaxy at different temperatures was measured using the technique of synchrotron radiation X-ray low angle reflection. The results indicate that the doped Sb atoms are distributed exponentially in the epitaxial layers, and the 1/e decay lengths are 0.45, 0.95 and 3.5 nm for the samples grown at temperatures of 250, 300 and 350 ℃, respectively. For samples grown at 400 ℃, the 1/e decay length of the Sb atomic distribution increases drastically because of the segregation of Sb atoms during the growth process.