Idiopathic pulmonary fibrosis (IPF) is a chronic and ultimately fatal disease characterized by a progressive damage of lung structure and decline in lung function.This study intends to carry out an open, single-center, non-randomized, self control phase I clinical trial. During the treatment, lung stem cells will be isolated from patients' own bronchi and expanded in vitro. Cultured cells will be injected directly into the lesion by fiberoptic bronchoscopy after lavage. After twelve-month observation, the investigators will evaluate the safety and efficacy of the treatment by measuring the key clinical indicators.