Abstract: With the increasingly stringent requirements for sewage treatment and the continuous improvement of public health awareness, the nitrate pollution in water body has caused widespread concern in the world. At present, biological heterotrophic denitrification as the main technical means to remove nitrate in water, the carbon source has been the key restricting factor, and the disadvantages of traditional external carbon source have also been found. Therefore, the development of new slow-release carbon source suitable for biological denitrification process has become the focus of attention of researchers at home and abroad. Starting from the necessity of developing slow-release carbon sources for promoting biological denitrification, the types of slow-release carbon sources, the effect of promoting denitrification, the modification methods, the influencing factors of nitrogen removal, the mechanism of action and the characteristics of biofilm were analyzed in detail. The denitrification promoting performance and biofilm community structure of natural slow-release carbon source, modified slow-release carbon source and synthetic slow-release carbon source were compared and revealed. At the same time, the prospects of breaking through the speed limiting steps of reaction kinetics, optimizing skeleton materials and spatial framework, developing new slow-release carbon sources and promoting biological denitrification process were put forward for the follow-up researches, so as to provide reference and basis for the dissemination and application of slow-release carbon sources to promote the efficiency of biological denitrification.