Objective To study the feasibility,effectiveness and safety of cryoablation in renal VX2 tumor.Methods Thirty-eight rabbits with renal VX2 tumor in right kidney were randomized into 3 groups:cryoablation group,nephrectomy group and tumor control group (15,15 and 8 respectively).Vein blood was taken at the same time point for to investigate SCr and BUN in cryoablation and nephrectomy groups.The tumors were also evalutated by two-dimensional ultrasonography and contrast enhanced ultrasonography for the changes of the size,shape and the echo pre-treatment and post-treatment (21st day) in cryoablation and tumor control groups.Rabbits were sacrificed on the 21st day after the treatment,and the metastasis rates were compared.Results ①Significant differences were noted in favor of pre-treatment versus post-treatment with regard to SCr (71.00± 11.33 versus 105.80± 18.66 μmol/L,P＜ 0.05),BUN (6.69±0.78 versus 8.52± 1.04 mmol/L,P＜0.05) in cryoablation group,and the 2 indexes returned to pretreatment level on the 14th day after cryoablation (P＞0.05).There were significant differences between cryoablation group and nephrectomy group on the 21 st day in levels of SCr (81.93±20.14 versus 103.20± 16.16 μmol/L,P＜0.05) and BUN (7.00±0.56 versus 8.36±0.76 mmol/L,P＜0.05).②On the post-treatment day 21,there was no significant difference in the rate of metastasis in cryoablation group and nephrectomy group (47％ versus 40％,P＞0.05).The volume of the tumor in cryoablation group was significantly smaller than that in tumor control group (1.35±0.24 versus 4.74± 1.69 cm3,P＜0.05).③There was no significant difference in monitoring oncologic efficacy between contrast enhanced ultrasonography and pathologic examination (P＞0.05).Conclusions Cryoablation is an effective,safe and feasible therapy in treatment of rabbit renal VX2 tumor.Contrast enhanced ultrasonography can be used as an effective method to evaluate the therapeutic efficiency of cryoablation in renal tumor.