ABC multidrug transporters play the main role in multidrug resistance(MDR) of cancer cells.RNA interference(RNAi) has been applied in the study of the mechanism and reverse of multidrug resistance of cancer cells.MDR cell lines of human salivary gland adenoid cystic carcinoma(ACC) and mucoepidermoid carcinoma(MEC) were established.MDR of the cells may be related to multigenes and MDR1 gene or ABCC1 gene may be most important.The expressions of MDR1 or ABCC1 gene and proteins of the cells can be silenced and the MDR can be overcome by RNAi.