Objective To investigate the internal environment changes of whole-body hypothermia on neonatal hypoxic-ischemia encephalopathy. Methods Twenty-nine hypoxic-ischemia encephalopathy neonates were randomized to either systemic hypothermia group(n=15) or normothermia group(n=14).The infants in hypothermia group were got parental consent and maintained rectal temperature 33.0℃~34.0℃ for 72 h by cooling.The other supportive treatments were the same in both groups.The dynamic changes of serum Ca²⁺,Na⁺,Cl^-,K⁺,PH,BE,ALT,AST,BUN,Cr,CK-MB at 0 and 72 hours after admission were monitored respectively. Results At the time of 72 h after admission,levels of serum Ca²⁺ and Na⁺ in systemic hypothermia group were higher than those in normothermia group;the level of serum CK-MB in systemic hypothermia group were lower than those in normothermia group;and levels of serum Cl^-,K⁺,ALT,AST,BUN,Cr,BE and PH were no differences between this two groups. Conclusion Systemic hypothermia on neonatal hypoxic-ischemia encephalopathy can improve hypocalcemia and hyponatremia,without aggravated damagements of liver,kidney and acid-base balance,even may have neuroprotective effects on damaged myocardium.