Abstract: Objective To investigate the effect of expression of miR-21 on the stem cell characteristics of human tongue squamous cell carcinoma and cisplatin sensitivity. Methods Human tongue squamous cell carcinoma SCC9 cells were cultured by adherent and suspension cultures to obtain SCC9a and SCC9f cells. The miR-21 mimics and miR-21 inhibitor were transfected to the SCC9f cells respectively. Stem cell related transcription factors （Oct3／4， Sox2， Nanog） and miR-21 expression was detected by quantitative real-time PCR（QPCR）. The proportion of ALDH positive cells was detected by ALDEFLOR kit. The cell proliferation was determined by MTT assay，and AnnexinV／PI method was used to measure cell apoptosis. Results The expression of Oct3／4， Sox2 and Nanog and the positive rate of ALDH in SCC9f cells was significantly higher than that of SCC9a cells. The inhibition rate and apoptosis ratio of SCC9f cells treated with cisplatin was lower than those of SCC9a cells. The expression of miR-21 in SCC9f was higher than that of SCC9a （P＜0.05）. The expression of miR-21 in SCC9m was higher than that of SCC9f （P＜0.05）， while that of SCC9i was lower than that of SCC9f （P＜0.05）. The expression of Oct3／4 in SCC9m cells was higher than that in SCC9f cells （P＜0.05）. The expression of Oct3／4， Sox2 and Nanog in SCC9i cells was significantly lower than that in SCC9f cells （P＜0.05）. The positive ratio of ALDH in SCC9a， SCC9m and SCC9i cells was significantly different from that in SCC9f cells （P＜0.05）. The apoptosis rate of SCC9f cells was lower than that of SCC9i cells，and higher than that of SCC9m cells （all P＜0.05）. Conclusion The SCC9f cultured by suspension culture method have stem cell characteristics， and more tolerable to cisplatin. Inhibition of miR-21 expression could enhance the sensitivity of SCC9 cells to cisplatin. It may be related to tumor stem cells which are regulated by the expression of miR-21.