In order to trace EMT status of lung cancer A549 cells，we constructed a lentiviral plasmid carrying E-cadherin gene promoter，which was co-transfected with packaging plasmids pVSVG and Δ8.91 into HEK 293T cells to produce active lentivirus. Then the A549 cells were infected by the collected lentivirus，and the success of infection was examined by flow-cytometry and Western blot. Afterwards，TGF-β was used to treat the infected A549 cell，and the expression of GFP and E-cadherin in those cells was detected by the fluorescence observation，RT-PCR and Western blot. We found that after 48 hours of TGF-β induction，the morphology of A549 cells changed from cobblestone to long fusiform. Fluorescence microscopy showed that fluorescence signal of A549 cells was significantly decreased in the induction group compared with untreated cells，and RNA levels and protein levels of GFP and E-cadherin were decreased as well. This indicated that the EMT tracer system was established successfully. In conclusion，we established a EMT tracer system using lentivirus in the A549 cells，providing materials for further study of EMT process of lung cancer.