Abstract: Objective To explore the relationship between normalization of tumor microvessels and CA9 for rh-Endostatin to inhibit Lewis lung cancer (LLC) and the expression level of CA9 in LLC. Methods Lewis cells of logarithmic growth phase were collected and made into 1×10⁶ mL^-1 cell suspensions were prepared. The transplanted tumor model of LLC was established on C57/BL6 mice by injected 0.2 mL cell suspensions/mice into 40 C57/BL6 mice. 40 LLC mice were randomly divided into control group and rh-ES group (20 mice per group). Control group experienced treatment of intraperitoneal injection (ip) for 0.2 mL NS/d, while rh-ES group was treated for 5 mg rh-ES/(kg·d) from the first to the ninth day. The samples of 5 mice were obtained from day 2, day 4, day 6 and day 9 after treatment in control group or rh-ES group, respectively. CA9 was tested by IHC in LLC and paracancerous tissues and estimated by RT-PCR and ELISA in the each time point of both rh-ES group and control group, respectively. Results The transplanted tumor model of LLC on C57/BL6 mice was established successfully. The expression of CA9 decreased on day 4 and day 6 in rh-ES group estimated by RT-PCR and ELISA, which indicated some great significance when compared with day 2, day 9 in rh-ES group and day 4, day 6 in control group (P<0.05), and the expression of CA9 in day 2, day 4, day 6, day 9 tested by IHC was higher in