Clostridium was isolated and characterized from powdered infant formula (PIF), whey protein concentrate (WPC) suspected to be contaminated with C.botulinum and WPC-based products, as well as PIF collected from Beijing market.Methods Clostridium isolates were characterized by morphological characteristics, gram′s stain, microscopic and electron microscopy characteristics, biochemical test, 16S rRNA sequencing and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) methods.Results Among 78 samples, 16(20.5%, including 2 WPC and 14 PIF) samples were contaminated with Clostridium. A total of 17 isolates were obtained, of which 12 isolates were identified as C.sporogenes, 2 isolates of C.beijerinckii, 2 isolates of C.butyricum and 1 isolate of C.tertium.Conclusion WPC imported from New Zealandand WPC-based PIF were heavily contaminated by Clostridium, and the most predominant species of Clostridium detected was C.sporogenes.