Abstract: Objective To analyze the small intestine bacterial overgrowth (SIBO) and related factors among Crohn disease (CD) patients in remission,and discuss the clinical application of hydrogen-methane breath test in CD patients. Methods The glucose hydrogen-methane breath tests was conducted among 25 CD patients in remission (CDAI<150) and 20 healthy people (control group).Based on testing result,CD patients in remission were further divided into SIBO positive and SIBO negative group.The symptom score (abdominal pain and abdominal distension),stool character,serum inflammatory markers (TNF-α,IFN-γ,IL-6 and IL-10) and oxidative stress related markers (GSH and LPO) among the three groups were compared statistically. Results ①The prevalence of SIBO (44%) among CD was significantly higher than that (5%) in control group (χ²=0.72,P<0.01).②Abdominal distension score among SIBO positive group was higher than that in SIBO negative group (P<0.05).There were no significant differences about abdominal pain score,stool frequency and character between the two groups (P>0.05),but significantly higher than that in the control group (P<0.01).Ages,course,location,behavior and CDAI scores were not correlated to SIBO.③GSH in SIBO positive group was lower than that in SIBO negative group (P<0.05).However,there were no significant differences about TNF-α,IFN-γ,IL-6,IL-10 and LPO between the two groups (P>0.05). Conclusions Compared with healthy people,the prevalence of SIBO is more common among CD patients,which may be one of reasons about the aggravation of digestive-related symptoms,especially abdominal distension.Intestinal microenvironment change and oxygen free radical removal may take part in the occurrence and development of SIBO.If patients are with positive SIBO,antibiotics and probiotics can be adopted.Because of the limited cases,more studies should be taken to identify the theory.