Objective To establish the method to express leukemia inhibitory factor(LIF) in fetal fibroblasts in order to provide theoretical foundation for establishment of transgenic animal model.Methods Using the fetal of 13.5 d ICR mouse,the primary fetal fibroblasts were cultivated by trypsin enzyme digestion.The lineared eukaryotic expression vector pcDNA3.1-LIF was transferred to the fetal fibroblasts of mouse with liposome induction.The positive cells were selected by G418,genome DNA of the positive cells was extracted and sequenced. Results The primary fetal fibroblasts of mouse were successfully obtained by isolating and culturing,and fetal fibroblasts expressing LIF were established by transferring.The sequencing result demonstrated that the homology of clone plasmid of positive cells was about 99%.Conclusion Eukaryotic expression vector pcDNA3.1-LIF is successfully transferred to the fetal fibroblasts of mouse.