Abstract: Objective To explore the feasibility of serum oxidative stress indices in early monitoring of pulmonary injury caused by silica dust and in judgment of coal workers.pneumoconiosis conditions.Methods Sixty-fourcoal workers and forty-five coal worker pneumoconiosis patients including 23 cases of phase I,19 cases of phase Ⅱ and 3 cases of phase Ⅲ were selected as participants.The vital capacity(VC),time vital capacity(FVC),forced expiratory volume in one second(FEV1)and FEV1/FVC% were measured and the activities of superoxide dismutase(SOD),catalase(CAT)and the levels of malondialdehy de(MDA)in serum were determined in all participants.Among the 64 coal workers,there were 34 tunneling workers as high exposure group,13 surface workers as moderate exposure group and 17 auxiliary workers as control group.Results Indices of serum oxidative stress and pulmonary ventilatory function were not statistically different between different categories of workers.Serum CAT levels were lower in phase I and phase Ⅱ patients than in coal workers(P<0.01,P<0.01).VC,FEV1 and FEV1/FVC of phase I patients,VC and FEV 1 of phase Ⅱ pat ients and FEV1 of phase Ⅲ patients were lower than those of coal workers(P<0.05,P<0.01,P<0.05,P<0.05,P<0.01,P<0.05).Results of Spear man rank correlation analysis showed that VC,FVC and FEV 1 were positive correlated with serum CAT and SOD levels(n=109,P<0.05).Conclusion Serum CAT and SOD levels can be used as reference indices for judg ment of coal worker pneumoconiosis conditions,but confirmative conclusion for early monitoring of pulmonary injury with the indices need to be studied.