Objective : To study the effect of ubiquinol⁃cytochrome C reductase subunit 2 (QCR2) on cell cycle arrest of cervical cancer SiHa cell line , and to explore related mechanisms. Methods : The log⁃phase SiHa cells were taken , and QCR2 siRNA and control siRNA were transfected into SiHa cells by liposome transfection , which were set as QCR2 siRNA group and control siRNA group , and untreated cells were set as a blank group. qRT⁃PCR and Western blot were used to determine the relative expression of QCR2 , p53 mRNA and protein. Propidium iodide(PI) staining was used to determine cell cycle. The cells in the QCR2 siRNA group were taken , and were intervened with a final concentration of 50 nmol/L ubiquitin⁃proteasome inhibitor PS341 as the QCR2 siRNA + PS341 group. In addition , the cells in the QCR2 siRNA group were intervened with the same amount of normal saline (NS) and set as the QCR2 siRNA + NS group. Western blot was used to determine the relative expression of p53 protein. The immunoprecipitation test was used to determine the level of p53 ubiquitination. Results : Observed under a fluorescence microscope , the transfection efficiency of QCR2 siRNA group and control siRNA group were both > 80% . Compared with the blank group and control siRNA group , the relative expression of QCR2 mRNA and protein in the QCR2 siRNA group decreased (P < 0. 05) , the proportion of G0/G1 increased (P < 0. 05) , and the proportion of S , G2/M decreased (P < 0. 05) . There was no significant difference in the relative expression of p53 mRNA between the groups. Compared with the blank group and control siRNA group , the relative expression of p53 protein in the QCR2 siRNA group increased (P < 0. 05) . Compared with the blank group and QCR2 siRNA + PS341 group , the relative expression of p53 protein in the QCR2 siRNA group and QCR2 siRNA + NS group increased (P < 0. 05) . Compared with the blank group and control siRNA group , the degree of p53 ubiquitination in the QCR2 siRNA group was reduced ( P < 0. 05 ) . Conclusion Silencing QCR2 can block SiHa cells in G0/G1 phase. Its mechanism may be related to the inhibition of p53 ubiquitination and the increase of its protein expression.