Abstract: Objective To investigate the exposure level of occupational hazards of welding operation environment in automobile manufacturing industry, and the adverse effects of welding fumes on the workers' respiratory system. Methods The monitoring data during 2007 to 2011 in two welding workshops and occupational health examination data of welding operators, workers in exposure to other fumes and the workers without any records of occupational exposure were collected and evaluated. Results The exposure level of both welding fume and manganese dioxide of workers in this enterprise from 2007 to 2011 was low but the concentration of welding fume at a few welding worksites from 2007 to 2009 and manganese dioxide from 2007 to 2010 was still higher than the national exposure limits. No case of pneumoconiosis was diagnosed till moment and the chest radiograph showed that there was no difference of abnormality rate among these different four groups(P>0.05). However, the self-reported abnormality of respiratory symptoms was significantly different in the years from 2008 to 2010 (χ²=8.73,10.97,11.31,P<0.05). The abnormality of lung function were significantly different in the year 2008,2009 and 2011 respectively(χ²=8.62,8.29,8.14,P=0.04). The exposed worker(including welding fume exposure and dust exposure) had higher abnormality than that of non-exposed workers. The pulmonary function damage of the exposed group was mainly manifested with restrictive pulmonary dysfunction. The lung function abnormality was positively relative to the working years. Conclusion Though the exposure level of welding fume and manganese dioxide was low in this enterprise, the exposed workers still had health problem including respiratory consciousness symptoms and reduced pulmonary function. Self-reported abnormality of respiratory symptoms and regular chest checkup will help control the damage to lungs resulted from inhalation of welding fumes. The abnormality of lung function was relative to the working years.