As a new type of fluorescent nanomaterials, carbon dots (CDs) have exhibited excellent photoluminescence properties with tunable emission and high quantum yields, hence they have attracted an increasing interest in diverse research areas. The photoluminescence performance of CDs is primarily influenced by their precursors, which directly or indirectly determine the structures and specific functions of the resultant CDs. In this review, we aim to summarize the recent progress on synthesis of CDs using small aliphatic molecules, anilines, polyphenol, polycyclic aromatic hydrocarbons, organic dyes, or biomass as precursors. The associations of the physical and chemical properties of the CDs with their respective precursors are comprehensively investigated, and the potential applications and future development of CDs are discussed in detail. It is hoped that this review will open new horizons for CDs preparation by rational selection of the precursors from the vastly available carbon sources and the critical comments presented, here could inspire and guide future research in the design of multifunctional CDs.