MicroRNA(miRNA) is a kind of small non-coding RNA which contents 18-25 nucleotide (nt). MiRNA plays an important role in human tumor of digestive system. Recently lots of research demonstrates that miRNA can act either as oncogenes or as tumor suppressor genes or sometimes as both. And many families of miRNAs'targets have been found. So the study of miRNA will supply a new way to the diagnosis and therapy of digestive diseases.