Long noncoding RNA (lncRNA) is a kind of noncoding RNA with length more than 200 nucleotides. The researches on lncRNA have increased rapidly, but the functions of most lncRNA are still unknown. With the help of Arraystar lncRNA chip analysis, we found that the expression of lncRNA21905 is significantly higher in mitosis than that in interphase, which indicate that lncRNA21905 may have function in mitosis. In this research, we depleted lncRNA21905 by siRNA, and found that knockdown of lncRNA21905 can induce obvious mitotic arrest in tumor cells. In addition, through the TANRIC database analysis, we also found that the prognosis of renal clear cell carcinoma (RCCC) patients with high expression of lncRNA21905 is poor. Above all, this research indicate that lncRNA21905 have an important function on the regulation of mitosis in tumor cells, which may provide a theoretical basis for further revealing its involvement in the prognosis of RCCC.