Abstract: Objective To investigate the effects of occupational stress and working conditions on diabetes mellitus(DM)in male police officers.Methods Totally 6 075 police offices in Tianjin municipality were recruited for a prospective cohort study on risk factors of DM.DM cases were screened during the period of the follow-up.Cox proportional hazard regression analysis was used to calculate the hazard ratios(HR) of DM predicted by occupational stress status and working conditions.Results During the follow-up period of 2.61 years(median)from 2008 to 2011,179(3.1%) persons developed DM among the participants.The risk of DM for traffic police was significantly higher than other police(HR=2.89,95%confidence interval95%CI:2.12-3.93).Compared to the police with moderate occupational stress,the HR of DM for the police officers without the stress or with high occupational stress were 3.12(95%CI:1.81-5.38)and 1.97(95%CI=1.34-2.91); compared to the police with appropriate occupational stress reaction,the HR for the police officers with moderate or high occupational stress reaction were 1.66(95%CI:1.12-2.44)and 2.57(95%CI:1.34-4.92),respectively.After redefined the risk factors,the results of Cox regression showed that the HR(95%CI)of DM for the traffic police without occupational stress,with moderate or high occupational stress,with moderate or high occupational stress reaction were 4.62(2.39-8.90),2.44(1.65-3.60),3.30(2.20-4.94),3.11(1.93-5.03),and 4.48(1.83-10.98)compared to other police officers,respectively.Conclusion Occupational stress and working conditions play an important role in the incident of DM in police officers and being a traffic police,without occupational stress,with moderate or high occupational stress,and with moderate or high occupational stress reaction are independent risk factors of DM.