Objective To observe the effects of mild hypothermia induced by pentobarbital sodium on hematology in male BALB/C mice. Method Healthy male BALB/C mice were divided randomly into two groups: control group(C) and mild hypothermia group(M).The body temperature of the mild hypothermia group was maintained between 28℃ to 30℃(anal temperature) for 4 hours induced by pentobarbital sodium injected intraperitoneally, then recover unaffected. Anal temperature, coagulation, electrolytes, and blood cell indexes were examined in 2, 24, 72 hours after treated by mild hypothermia; Control group was given equal volume of saline volume at constant temperature. Results The body temperature and coagulation in mild hypothermia group showed no significant difference compared with the control group(P>0.05),but the concentration of K⁺ and Na⁺ in mild hypothermia group were higher than control group(P<0.01), the number of WBC in mild hypothermia group was lower than control group(P<0.01或P<0.05), and the RBC、HGB、MCH、MCHC in mild hypothermia group were lower than control group transiently(P<0.01或P<0.05). Conclusion Mild hypothermia induced by pentobarbital sodium affects some of hematological values in mice considerably.