Abstract: Based on the previous results of contamination survey on a coking plant in Beijing, the effects of uncertainty of 15exposure parameters and soil pollutant concentrations on human health risk assessment of benzene and benzopyrene were investigated with the methods of probabilistic risk assessment (PRA). Results showed that the risk values of PRA, which was located at the 95^th centile in the probabilistic range of risk values, were lower than that of deterministic risk assessment (DRA) of benzene and benzopyrene in both surface and subsurface soil through single and total exposure pathways. The total risk calculated by PRA ranged from 1.5×10-8 to 6.9×10-3 for benzene and 2.3×10-9 to 2.2×10-3 for benzopyrene, and the values were located at the 95^th centile in the probabilistic range of risk were 3.8×10-4 and 1.1×10-4, respectively. The total risks conducted by DRA were located at the 96.8^th and 99.1^th centiles in the probabilistic range of risk, which were 1.5and 3.2times of the values by PRA. This indicated that the methods of DRA overestimated the real risk. The results of parameter sensitivity analysis revealed that the concentration of benzene in the subsurface soil (94.63%) and the adult exposure duration (4.12%) contributed the most to the uncertainty in benzene risk assessment, and the concentration of benzopyrene in the surface soil (92.3%), adult exposure duration (2.40%), soil ingestion rate (2.12%) and child exposure duration (1.21%) contributed the most to the uncertainty in benzopyrene risk assessment.