OBJECTIVE To explore the effects of irbesartan（Irb）combined with 5-fluorouracil（5-FU）on the proliferation and extracellular signal-regulated kinase （ERK）/peroxidase proliferator-activated receptor γ（PPARγ）signaling pathway of Lewis lung cancer cells. METHODS Lewis lung cancer cells from mice were divided into normal control （NC）group，Irb low-dose （LD）group（1×10－3 mmol/L），Irb high-dose （HD）group（1×10－1 mmol/L），5-FU group （10 μmol/L），Irb LD+ 5-FU group （Irb 1×10－3 mmol/L+5-FU 10 μmol/L）and Irb HD+ 5-FU group （Irb 1×10－1 mmol/L+5-FU 10 μmol/L）. MTT method was used to measure the activity of cell proliferation in each group. Plate colony formation experiment was used to determine the number of cell colonies formed in each group ；Western blot method was used to detect the expression levels of proliferating cell nuclear antigen （PCNA），p53，ERK1/2，p-ERK1/2 and PPAR γ protein in each group. RESULTS Compared with the NC group ，the cell proliferation activity ，the number of colonies formed and the protein levels of PCNA ，p-ERK1/2，and PPARγ were significantly reduced in the other five groups ，and the protein level of p 53 was significantly increased （P＜0.05）；the protein expression of ERK1/2 had no significant difference （P＞0.05）. The changes of above indexes in Irb LD+ 5-FU group and Irb HD+ 5-FU group were more significant than Irb LD group ，Irb HD group and 5-FU group （P＜0.05）. CONCLUSIONS Irb combined with 5-FU can inhibit the proliferation of Lewis lung cancer cell ，and the effect is better than that of the two alone. The mechanism may be related to the inhibition of ERK/PPARγ signal pathway.