Sr-containing alpha-SiAlON (Srm/2Si12-m-nAlm+nOnN16-n:Eu2+) phosphor was obtained as a major phase in compositions having small m and n values, by firing the powder mixture of SrSi2, SrO, alpha-Si3N4, AlN, and Eu2O3 at 2000 degrees C for 2 h under 1 MPa nitrogen atmosphere. The crystal structure of Sr-alpha-SiAlON was refined by the Rietveld analysis of the synchrotron X-ray powder diffraction pattern. The crystal structure showed that the Sr-N2 bonding distance of Sr-alpha-SiAlON was fairly large compared with that of Ca-alpha-SiAlON. The displacement of N2 sites probably allow the interstices in alpha-SiAlON to accommodate the introduction of the large Sr ion. Sr-alpha-SiAlON:Eu2+ phosphor has an excitation wavelength ranging from the ultraviolet region to 500 nm and emits a strong yellow light.