Abstract: Coal tar pitch (CTP) contains a large number of polycyclic aromatic hydrocarbons (PAHs) that are harmful to the ecological environment, which limits its application and development. Therefore, reducing or inhibiting the release of toxic PAHs in CTP has become an urgent problem to be solved. Microwave and UV-assisted 10-undecenal were used to modify CTP with potassium bisulfate as a catalyst. The variation of benzo［a］pyrene equivalents of 16 U.S. Environment Protection Agency (EPA) priority PAHs before and after modification were also evaluated. In the modified CTP, the maximum removal rateof 16 priority PAHs reached 91.59% within 60~90 minutes and the total content was reduced to below 7.41 mg/g, which saved 2.5 to 3 hours compared with no auxiliary reaction. The characteristic analysis of infrared, Raman, X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (13C CP/MAS NMR) of CTP before and after modification showed that in the process of intensive modification experiments, 10-undecenal and polycyclic aromatic hydrocarbons undergo an electrophilic substitution reaction, occupying toxic sites or changing the structure of toxic PAHs, thereby reducing the quality of 16 priority monitoring toxic PAHs concentration.