OBJECTIVE:To study the correlation between RRM2 expression of cervical cancer cell line C33a and Siha and cell sensitivity to gemcitabine(Gem). METHODS:C33a and Siha were treated with 0.1-3.2 μmol/L and 0.5-512 μmol/L of gemcitabine respectively for 72 h;cell viability was measured by MTT assay to calculate the value of IC50. The expression of RRM2 was mea-sured by Western blot and RT-PCR. Siha cell was treated with gradient concentration and large dose of Gem to establish Siha/Gem drug-resistant cell line. RNA interference technology knockdown the expression of RRM2 in Siha/Gem cell,and IC50 of Gem to cell was determined before and after knockdown. RESULTS:The IC50 values of Gem to Siha and C33a were 16.8 μmol/L and 0.63μmol/L. Compared with C33a cells,the expression of RRM2 in Siha cell was higher. Compared with Siha cells,Siha/Gem drug-re-sistant cell(drug resistant index of 16.26)showed higher RRM2 expression. Siha/Gem drug-resistant cell knockdown RRM2,IC50 of Gem to it was decreased,and inverse drug resistant times was 4.24. CONCLUSIONS:There is an negative correlation between RRM2 expression and Gem sensitivity in cervical cancer cell lines. The knockdown of RRM2 in Siha/Gem increases the sensitivity to Gem.