CuIn(S,Se)2 (CISS) powders with varying S/S + Se ratios were synthesized by mechanochemical process (MCP) and a self -propagating combustion occurred during milling. Influence of S content on the structure was investigated by X-ray diffraction and Raman spectroscopy. Morphology of CISS powders was investigated by scanning electron microscopy (SEM). Characteristic peaks of the chalcopyrite structure are clearly observed and CISS (112) peaks shifts to higher value as S content was increased. Lattice constants for CISS samples decrease with the S content increased. Moreover, the large size mismatch between S and Se atoms leads to the lattice parameters negative deviate from Vegard's law. The Raman A1 mode of the chalcopyrite CISS has been observed, and InxSey and CuS has been also detected in some samples. The morphology observation of CISS powders shows that the uniformity of particle size distribution decreases with increasing sulfur content. The ignition time of Cu-In-S-Se self-propagating reaction was extended with the increase of sulfur content and the possible reason has been explained. Furthermore, the reaction mechanism of Cu-In-S-Se system has also been discussed.