Objective To investigate the impact of injection of acetic acid hypertonic saline solution (AHS) in dog liver during radiofrequency ablation (RFA) on its destructive zone. Methods RFAs were performed in dog livers by using LDRF-120S mutiple probe ablation system combining 50% acetic acid 5% hypertonic saline solution injection. Thirty healthy adult hybrid dogs were randomly divided into 5 groups (n=6). Group A: RFA was performed immediately after injection of 2 ml AHS; Group B: RFA was performed 5 min after injection of 2 ml AHS; Group C: RFA was performed immediately after injection of 4 ml AHS; Group D: RFA was performed 5 min after injection of 4 ml AHS; Group E: RFA was performed immediately after injection of 6 ml AHS. Results There were no significant differences in the mean initial impedance within 5 groups. The mean ablation times were different significantly among 5 groups (F=83.831, P＜0.001). The mean ablation time was different significantly between any two groups by LSD-t analysis (P＜0.001). The mean coagulation diameters were different significantly among 5 groups （F=53.488, P＜0.001）. The mean coagulation diameter of group E was the largest among 5 groups. Besides mean coagulation diameter was no significant difference between group D and E (Pgt;0.05), the mean coagulation diameter was different significantly between any two groups by LSD-t analysis (P＜0.001). Obviously thrombus were shown in coagulation necrosis zone and nearly normal tissue with gordon amp; sweet. AHS spillage from the injection site occurred in group E. Four dogs died in group E within 14 d but no dog died in the other groups. Conclusion RFA is performed 5 min after injection of 4 ml AHS in dog liver produces the ideal ablation destructive zone.