Objective To determine the degrees and types of bacterial contamination in home-expressed mothers milk for preterm admitted to neonatal unit in China.Methods The present paper was a descriptive study enrolled a total of 75 human breast milk samples from February 2nd to March 1 st 2015.The primary outcome was microbiological features of breast milk samples collected at home.A sample of more than 104 colony-forming units/mL is considered as the significantly bacterial contaminated breast milk.Results Among the milk samples obtained from the mothers of 75 neonatal babies,69.3 ％ had substantial bacterial growth.This high contamination rate could be due to the Chinese tradition of avoiding bathing for one month after childbirth.Conclusion Un-processed breast milk expressed by mothers in home was not safe for high risk preterm babies.Health care needs to pay attention to the risk of that in China.Good hygienic practice and strict process control for breast expression,including collection,transportation and storage should be developed for Chinese mothers of hospitalized preterm infants.