Abstract： Objective To explore the effects of hemofiltration on serum enzyme (SE),endotoxin (ET) and malonaldehyde (MDA) of dogs with heat stroke caused shock.Methods Sixteen healthy male hybrid dogs were randomly divided into 2 groups,8 for each:as heat stroke group (HS group ) and hemofiltration group (HF group).Severe heat stroke model was induced with high temperature.The dogs were taken out of the heating cabin when it reached heat stroke level,and then observed under normal temperature without treatment.The dogs in HF group was immediately treated with hemofiltration.The changes of SE,ET,MDA of two groups of dogs were observed and the survival time between two groups was compared,Results The time from heat exposure to shock was ( 107.00 ± 28.52 ) and ( 111.38 ± 22.24 )minutes in HS group and HF group respectively ( t =- 0.354,P =0.729 ).The SE ( CK,LDH,ALT,AST) of the dogs were all higher after heat stroke,and the dogs of two groups showed no siginificant difference (P ＞ 0.05).At three hours after heat stroke,the SE increased apparently in HS group and HF group,but the level was significantly lower in HF group. Before heat stroke,the serum ET showed no siginificant difference between two groups ( P ＞ 0.05 ).After heat stroke,the serm ET was much higher than before ( P ＜0.01 ),but there was still no siginificant difference between two groups ( P ＞0.05 ).At three hours after heat stroke,the ET increased both in HF group and HS group,but the level was lower in HF group.Before heat stroke,the serm MDA had no siginificant difference between two groups ( P ＞ 0.05 ).After heat stroke,the serm MDA was much higher than before ( P ＜ 0.0l ),but there was still no siginificant difference between two groups (P ＞ 0.05 ).After heat stroke in three hours,the MDA of HS group rose apparently while HF group slowly declined.The median survival time of HF group was 180 min while HS group was 75 min,the survival rate showed siginificant difference (P ＜ 0.01 ).Conc4usions HF can improve the prognosis of dogs with heat stroke caused shock,prolong its survival time,reduce mortality.The mechanism is probably that HF clear serum MDA,partially clear serum ET and then eventually reduce cell and tissue injury and reduce SE.