Abstract: Microorganism in infant feces was analyzed using matrix-assisted laser desorption/ ionization time of flight mass spectrometry ( MALDI-TOF MS ) and high performance liquid chromatography mass spectrometry (HPLC-MS). Seventy samples from 0 to 3 years old infants were pretreated and analyzed by the two methods, and the results were compared. MALDI-TOF mass spectra indicated that ions observed increased with the infants′ age, more microorganisms were detected in 2-3 years old infant feces than that from 0-2 years old. HPLC-MS results indicated that the main microorganism in 0-1years old infant feces were Escherichia coli（E. coli）, Streptomycetaceae, yeast, monilia albican and streptococcus. The high abundance microorganism in 1-2 years old infant feces were red hair fungus bacteria, E. coli, monilia albican, yeast and and 2-3 years old infant feces were bifidobacterium, streptococcus, candida and E.coli.

Key words: infant feces, microbial diversity, MALDI-TOF MS, HPLC-MS