Abstract: 3,6-Dimethylphenanthrene (3,6-DMP) is a type of emerging contaminant widely present. Understanding the desorption process of pollutants in sediments is crucial for evaluating the transport and transformation patterns of pollutants. Herein, the effects of exogenous black carbon addition on the desorption process of 3,6-DMP in sediments were investigated. The addition of black charcoal led to a tighter agglomeration of sediment particles and significantly inhibited the desorption of 3,6-DMP. Among them, the addition of bamboo charcoal and coconut shell charcoal reduced the desorption rate of 3,6-DMP by 18.1% and 30.3%, respectively. Thermodynamic analysis showed that it was a spontaneous heat absorption reaction. The desorption process can be categorized into three phases: fast rise zone, slow rise zone and smooth zone. The limiting factor for 3,6-DMP desorption is chemisorption between sediment and PAHs through hydrogen, ligand and chemical bonds, followed by pore scale effect and concentration difference or free diffusion drive. Strong acidic and alkaline conditions inhibited 3,6-DMP desorption, while low salinity and oxygen promoted 3,6-DMP desorption. The results of this study are important for the study of desorption mechanism and influencing factors of emerging contaminants such as SPAHs.