The structure of the incommensurate composite crystal with composition Sr8/7TiS2.84 prepared in reductive atmosphere has been analyzed on the basis of the four-dimensional superspace-group approach using the powder X-ray diffraction data and the Rietveld analysis process. The crystal is composed of interpenetrating two parts, columns of face-shared TiS3 polyhedra and Sr rows packed among TiS3 Columns. The details of the structures Of Sr8/7TiS2.84 and Sr8/7TiS3 are compared, and the variation of the structure with the S content is discussed. (C) 2004 Elsevier B.V All rights reserved.