Objective To investigate the protective effect of coenzyme Q10 (CoQ10) in the liver of preeclampsiapregnant rats and the potential etiology. Methods Fifty pregnant SD rats were equally divided into the normal pregnant (NP) group (n=10) and the preeclampsia (PE) group (n=40) randomly. The PE rats (n=40) were equally divided into four groups randomly,distilled water(DW)group,CoQ10 group, CoQ10 combined magnesium(CM) group and magnesium (Mg) group were established by treating the preeclampsia rats on day 15 to 21 of gestation with different measures. As for all the 50 rats, systolic blood pressure (SBP) of rat tail was detected on day 10, 15 and 21 of gestation respectively, 24 hours proteinuria analysis were detected on day 10, 15 and 21 of gestation respectively, levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) in blood andsuperoxide dismutase (SOD), glutathione peroxidase (GSH-PX), malondialdehyde (MDA), caspase-3, Bcl-2 and Bax protein expression in liver tissue were detected by western blot assay on day 21 of gestation. Results (1)SBP and 24 hours proteinuria analysis:there was no statistic difference among all the five groups on day 10 of gestation (P>0.05). Whereas, SBP and 24 hours proteinuria analysis were significantly higher in CoQ10 group, CoQ10 combined CM group, CM group and DW group than that in NP group on day 15, 21 of gestation (P<0.05). And SBP and 24 hours proteinuria analysis were significantly lower in CoQ10 group, CoQ10 combined CM group and CM group than that in DW group on day 21 of gestation (P<0.05). (2) Liver function: among CoQ10 group, CoQ10 combined CM group, CM group, DW group and NP group, serum levels of ALT were respectively(52±7),(34±9),(49±10), (70 ± 19),(30 ± 7)U/L;and serum levels of AST were respectively(169 ± 25),(84 ± 11),(159 ± 20),(281 ± 26)and(78±18)U/L. ALT and AST serum levels were significantly higher in CoQ10 group, CM group and DW group than that in NP group (P<0.05). ALT and AST serum levels were significant lower in CoQ10 combined CM group than those in CoQ10 group, CM group and DW group, respectively (P<0.05). ALT and AST serum levels were significant lower in CoQ10 group and CM group than that in DW group, respectively (P<0.05). (3) SOD, GSH-PX, MDA, caspase-3, Bcl-2 and Bax expression in liver tissue of rats: SOD expression was significant higher in CoQ10 group, CoQ10 combined CM group than thoes in CM group, DW group and NP group(P<0.05);SOD expression was significant lower in CM group, DW grouo than thoes in NP group(P<0.05);and SOD expression was significant higher in CM group than that in DW group(P<0.05). Compared with CoQ10 group, CoQ10 combined CM group, CW group and DW group respectively, the GSH-PX and Bcl-2 protein expressions were significant higher in NP group(P<0.05), while MDA, caspase-3 and Bax protein expressions were significant lower in NP group(P<0.05);compared with CoQ10 group, CoQ10 combined CM group and CW group respectively, the GSH-PX and Bcl-2 protein expressions were significant lower in DW group (P<0.05), while MDA, caspase-3 and Bax protein expressions were significant higher in DW group (P<0.05). Conclusions Oxidative stress and apoptosis levles were upregulated in PE pregnant liver tissues. CoQ10 could effectively protect the liver by improving the liver functions and decreasing the apoptosis of liver cells in PE pregnant rats, and markedly decrease the oxidative stress and apoptosis in the livers. The protective roles of CoQ10 in liver might through its function of anti-oxidative stress and inhibiting cell apoptosis by regulating the balance of Bcl-2/Bax.