CASE PRESENTATION: A 71 years old female patient was admitted with cough since Jan 2012. On Chest CT (Feb 2012) bilateral diffuse ground-glass opacity/reticular opacities were observed. Open-lung biopsy (Feb 2012) confirmed hypersensitivity pneumonitis. Then patient was accepted 40 mg/day oral prednisolone therapy, then Clinical improvement was achieved and Chest CT (Apr 2012) was better. In Oct 2012 (2 months after stop pred) patient coughed again, with the bilateral ground-glass/reticular opacities on Chest CT worsing, The patient was admitted to our hospital Dec 2012 and was treated with pred 40mg/d since Jan 2013, then cough got better. But on Jan 13, 2013, she was admitted with fever, cough, white sputum, dyspnea again. Physical examination: there were bilateral moist rales, a little wheezing. We diagnosised as HP with infection, treated with ceftazidime and levo until symptoms relieved. After 12 weeks of treatment, the pred dose decreased gradually, eventually 10mg/d maintained. There were still shortness of breath after obvious activities and Chest CT had no obvious improvement. Patients did not find a clear source of allergies.