Objective:To summarize the clinical characteristics and laboratory diagnostic methods of infant botulism caused by Clostridium botulinum type B. Methods:Clinical data of 3 infants with type B botulism who were admitted to Children′s Hospital Affiliated to Capital Institute of Pediatrics from May to November 2018 were retrospectively analyzed. Botulinum toxin was detected in fecal samples or fecal enrichment solution of the patients, and Clostridium botulinum was cultured and isolated from fecal samples. Results:The age of onset of the patients (two boys and one girl) was 3, 3 and 8 months old, respectively. Two cases had the onset in May and one case had the onset in November. There were two cases with mixed feeding and one case with breast feeding. One case′s family members engaged in meat processing. All of them were previously healthy. All the children presented with acute flaccid paralysis, cranial nerve involvement and difficult defecation. Two cases had secondary urinary tract infection. Electromyograms of two cases showed that action potential amplitude of the motor nerve were lower than those of their peers. After treatments including intravenous human immunoglobulin, respiratory tract management, urethral catheterization, nasal feeding, etc., three cases recovered completely 2 to 4 months later. Type B botulinum toxin was detected in the fecal diluent of one patient, and the TPGYT enrichment solution and cooked meet medium of the feces of 3 patients, respectively. Clostridium botulinum B was identified from the feces of 3 infants after culture, isolation and purification. Conclusions:Combined with typical clinical manifestations including acute flaccid paralysis, cranial nerve involvement symptoms and difficult defecation examination, infant botulism can be clinically diagnosed. The detection of fecal botulinum toxin and the culture and isolation of Clostridium botulinum are helpful for the diagnosis.