Abstract: Objective To explore the different classification method of risks caused by hydrogen sulfide (H₂S) exposure at various workplaces. Methods The formula,R=S L was used to determine the risk, where the S represents the severity and the L represents the likelihood of harms. The severity was given for various workplaces based on the previous records of H₂S which caused deaths in different industries. The likelihood was estimated by the professionals according to the reality of 6 items which are the predominant causes for H₂S poisoning. The professions examined the workplaces and gave their scores. Results Using this formula, the risk caused by hydrogen sulfide exposure in common industries, such as emergency repair of drainpipes in the city, was classified. And it is easy for managers to clearly take the corresponding measures. Conclusion This risk classification method provides a unified,simple and workable way for the managers to estimate the risk at different workplaces. Of course, it needs to be improved in the future.