Breast milk is a complex liquid that enriched in immunological components and affect the development of the infant immune system. Exosomes, the membranous vesicles of endocytic origin, are ubiquitously in various body fluids which can mediate intercellular communication. MicroRNAs (miRNAs), a well-defined group of non-coding small RNAs, in human breast milk are packaged inside exosomes. Here, we present the identification of miRNAs in human breast milk exosomes using deep sequencing technology. We found that the immune-related miRNAs are enriched in breast milk exosomes, and are resistant to the general harsh conditions. Four small RNA libraries in human breast milk exosomes from four healthy women (30 +/- 0.9 years old, primiparity) when the infant were aged at 60 days were sequenced.