Abstract: Indoor simulation combustion experiments were performed using a dilution tunnel sampling system. The emission characteristics of PCDD/Fs in PM_2.5 from domestic biomass and coal combustion were analyzed using isotope dilution high-resolution gas chromatography/mass spectrometry (HRGC/HRMS), with subsequent calculation of emission factors. By integrating China's fuel consumption and population density data, we developed a "bottom-up" emission inventory for PM_2.5-bound PCDD/Fs from domestic biomass and coal combustion in China. The key findings are as follows: (1)The mass concentrations of PCDD/Fs in PM_2.5 from domestic biomass and coal combustion ranged from 0.181 to 4.7 pg/m³, with international toxic equivalent (I-TEQ) concentrations of 0.081 to 2.3 pg I-TEQ/m³. Congener analysis revealed that 2,3,7,8-T₄CDD (P < 0.01, R² = 0.90) showed strong correlations with I-TEQ concentrations, suggesting its potential as reliable toxicity indicators for PM_2.5-bound PCDD/Fs from domestic biomass and coal combustion. (2)The mass-based emission factors of PCDD/Fs in PM_2.5 were 1.82 ±0.97 ng/kg for biomass combustion and 4.09 ±2.76 ng/kg for coal combustion. The corresponding I-TEQ emission factors were 0.40 ±0.21 ng I-TEQ/kg (domestic biomass) and 0.53 ±0.24 ng I-TEQ/kg (domestic coal). (3)In 2021, the total emissions of PCDD/Fs in PM_2.5 from domestic biomass and coal combustion reached 90.0 g I-TEQ. With spatial analysis showing emission hotspots (>8 μg I-TEQ/km²) concentrated in Northeast and East China. Comparative analysis revealed these emissions were 0.2 times those from waste incineration (22.56 g I-TEQ) but 1.5 times higher than industrial combustion sources (208 g I-TEQ), highlighting domestic biomass and coal combustion as a significant PCDD/Fs emission source. (4)The estimated inhalation cancer risks were (9.5 ±7.2)×10^-5 for domestic biomass combustion and (3.1 ±1.7)×10^-5 for domestic coal combustion, representing 3.3-fold and 1.1-fold increases respectively over occupational exposure risks for industrial workers ((2.88 ±2.45)×10^-5). (conclusion)This study demonstrates that domestic biomass and coal combustion represents a substantial source of atmospheric PCDD/Fs in China, with significant public health implications. Our findings provide critical data to support targeted emission control strategies and public health interventions.