Objective:To establish the multidrug resistant animal model of CT26 colon cancercells in mice with the use of chemotherapy. Methods:CT26 colon cancer cells were injected subcutaneously into the right oxters of the mice.Fluorouracil and doxorubicin were combined into chemotherapy.Drown growth curve and calculate doubling generation time,chemotherapeutics drug sensitivity and drug fast index number of the tumor cells before and after chemotherapy were evaluated by MTT method.Levels of MDR1b mRNA were measured by RT-PCR.Eliminate function of P-gp were measured by flow cytometer.Results:Doubling generation time of the persister was higher than the parent cells.Drug resistance indexes were 29.3,26.4,10.9,7.0,5.8,3.0、and 2.8 respectively to ACT,ADM,VCR,HCPT,5-Fu,DAM,and VP16 after chemotherapy and the drug sensitivity were lower.The levels of MDR1b mRNA increased after chemotherapy and P-gp excretive ability was higher than that of no chemotherapy group.Conclusion:The multidrug resistant animal model has established successfully,which provided animal model for our study and research in the acquired multidrug resistance,and established groundwork for the research in increasing the chemotherapy effect.