Graphene-semiconductor nanocomposites, considered as a kind of most promising photocatalysts, have shown remarkable performance and drawn significant attention in the field of photo-driven chemical conversion using solar energy, due to the unique physicochemical properties of graphene. The photocatalytic enhancement of graphene-based nanocomposites is caused by the reduction of the recombination of electron-hole pairs, the extension of the light absorption range, increase of absorption of light intensity, enhancement of surface active sites, and improvement of chemical stability of photocatalysts. Recent progress in the photocatalysis development of graphene-based nanocomposites is highlighted and evaluated, focusing on the mechanism of graphene-enhanced photocatalytic activity, the understanding of electron transport, and the applications of graphene-based photocatalysts on water splitting, degradation or oxidization of organic contaminants, photoreduction of CO2 into renewable fuels, toxic elimination of heavy metal ions, and antibacterial applications.