Abstract: Objective To explore the effect of endogenous H2S in Idiopathic Pulmonary Fibrosis(IPF) patients, and its relationship with the severity of IPF. Methods Plasma H2S in 27 patients with IPF（IPF group）and 28 healthy physical examination people (control group) were tested. PaO2，ESR，CRP，LDH，HRCT and lung function in IPF group were tested to evaluate the severity of the disease at the same time. Then the concentrations of H2S in aggravating and palliative period in IPF group were observed. Results ⑴ Compared with the control group, the concentration of plasma H2S in IPF group was reduced significantly (P﹤0.01). ⑵The concentration of H2S in aggravating period was higher than palliative period (P﹤0.01). ⑶With the progress of HRCT，there was a descending trend of plasma H2S (P>0.05). Conclusion Endogenous H2S was probably involved in the course of IPF, and was associated with the progress of the disease.

Key words: Idiopathic Pulmonary Fibrosis, Hydrogen Sulfide