Objective To construct a gemcitabine-resistant variant of the breast cancer cell line (4T1/Gem) and establish a nude mouse model of breast cancer with hepatic metastatic. Methods A gemcitabine-resistant variant of the breast cancer 4T1 cell line was induced by gradually increasing the concentration of gemcitabine; this variant is referred to in this study as 4T1/Gem. The proliferation suppression rates of 4T1 and 4T1/Gem cells were determined by using the CCK-8 essay to evaluate the drug resistance indices of the cell lines. Western blot analysis was used to detect P-gp protein expression. Under ultrasonography, a 4T1/Gem cell suspension was injected into nude mice to induce liver tumors. H&E staining was used to observe tumor pathology, and immunohistochemistry was used to detect the expression of ER, PR, HER-2, Ki-67, and P-gp. Results After 14 months of induction, a 4T1/Gem cell line is established successfully. The cell line can grow stably in culture liquid containing 40 μg/ml gemcitabine. The drug resistance index of 4T1/Gem is 788.547. Compared with the 4T1 cell line, the 4T1/Gem cell line can upregulate P-gp protein expression and successfully establish a nude mouse model of breast cancer with hepatic metastatic. ER, PR, and HER-2 proteins exhibit negative expression in the tumor tissue. The positive expression of P-gp and 10% of Ki-67 proteins is also observed. Conclusion This study successfully constructs a gemcitabine-resistant variant of the breast cancer cell line (4T1/Gem)and establishes a nude mouse model of breast cancer with hepatic metastatic, thereby providing an experimental basis for developing and treating a drug-resistant variant of breast cancer.