Carbon dots (CDs) have received much attention due to their superior properties including water solubility, low toxicity, biocompatibility, small size, fluorescence, and ease of modification. The use of a more environmentally friendly method to prepare high‐quality CDs is still an urgent question waiting for solve. The use of renewable, inexpensive, and green biomass resources not only meets the urgent need for large‐scale synthesis biomass CDs (BCDs), but also promotes the development of sustainable applications. In this article, we summarize the representative methods for synthesizing BCDs in green and simple ways using biomass as a carbon source, including hydrothermal carbonization, and microwave, pyrolysis. The prepared BCDs have a uniform particle size distribution and a relatively high throughput, which provide a method to scale up industrial production. Moreover, the integration of specific optical properties, that is, tunable photoluminescence and up‐photoluminescence, has led to remarkable use in bioimaging, sensing, and drug delivery. But the current review is not particularly comprehensive for BCDs. Therefore, we now provide a review focusing on the synthesis, properties, and recent advances in BCDs in biosensing, bioimaging, optoelectronics, and catalytic applications. In this manuscript, the synthesis methods of BCDs prepared with biomass as a carbon source are introduced, and their properties and applications in various aspects are introduced. In this diagram reflects the properties and applications of BCDs.