Abstract: Objective To understand the risk rank of occupational hazards within an enterprise, the occupational health risk assessment was done. Methods Graham method(LEC),which was widely used in the safety risk assessment, was modified and used in this health risk assessment of a construction project with flue gas denitration within a electric power enterprise. Results The assignment of 3 important parameters, the probability of event occurrence,the frequency of hazard exposure and the severity of consequence,were studied in detail to determine the half quantitative risk assessment model of these occupational hazards. The results derived from this model showed that the health risk level of ammonia, carbon monoxide, sulfur dioxide, nitric oxide, nitrogen dioxide and the heat stress were ranked as stage Ⅱ,while the health risk level of noise and power frequency electromagnetic field were ranked as stageⅠ, which were consistent with the results determined by the experts. Conclusion This method could not only give half-quantitative risk level of occupational hazards in the design stage,but also be used to verify and correct the risk level in the running phase. These results will provide the reference for management and supervision of the occupational hazards.