Abstract: Objective: This article reported the study of lung function tests in thoracic sarcoidosis patients.Methods: Retrospectively analyzing the results of lung function tests in different periods and the effects of glucocorticoid in 40 thoracic sarcoidosis patients.Results: The results showed that these patients had restrictive ventilating obstacles with decreased DLCO and deterioration of small airway function parameters There were obvious decreasing in PaO 2 and increasing in ph,and PaCO₂ also revealed the decreasing tendency The curative results with dehydrocortisone demonstrated that MMF had largely improved in these thoracic sarcoidosis patients,and other lung function parameters,such as VC, RV, RV/TLC, MVV, FEV 1, DLCO, also showed the tendencies of turning better.Conclusion: We concluded that VC, RV, MMF, DLCO, DLCO/VA had the values of evaluating the progress of thoracic sarcoidosis,and there was a good value for MMF in evaluating the effects of glucocorticoid for thoracic sarcoidosis patients