Objective To investigate the effect of fluid resuscitation on hemodynamics in dogs with hemorrhagic shock at the initial stage of getting high altitude. Method he models of severe hemohagic shock were established in 13 mongrel dogs after they were brought to the high altitude a/ea and were mndondvvided inIo 3 group: LR group(n=3),6% HES group(n=5)and control group(n=5).The dogs in LR group wefe intravenously infused with lactated Ringers solution in 1.5 limes exsanguinated volume;those in 6% HES group were given hydroxyethyl starch in equal volume of exsanquination. A drop of solution waft noven to dogs in con,trol group.One hour after restritation,lactated Ringers solution waft infused at 5 Ilps as maintenance dose.The hemodynmnic variables were recorded.Results All animals in control group died two hour later.In LR group,the hemedynamie variables including MAP,CO,PAWP,CVP,LVSWI and RVSWI two hours after infiion were signifieantly higher than those.one hour after infusion(P<0.05),while HR,SVRd PVR were significantly lower(P<0.05).In dogs of 6% HES group,CO,PAP,PAWP,CVP,SVR and PVR two hours after infusion were significantly higher than those one hour after infusion(P<0.05),but MAP.HR.CI,LVSWI and RVSWI were not significantly different(P>0.05).Conclusions All of three doith hen rhagic shock would die(3/3)at the initial stage of being brought to high altitude alles without fluid resuscitation. Fluid resuscitation with LR solution 1.5 times the exsanquinated volume was effective and safe. The infusion of 6% hydroxyethyl starch at equal volume of exsanqination may easily cause heart failure or pulmonary edema.