Objective:To observe the protective effect of the extract of Adiantum capillus-veneris L. on cardiac tissue of rat model with chronic mountain sickness (CMS). Method A total of 50 rats were randomly divided into different groups namely plain control group(CG),high altitude model group(MG),nifedipine positive control group(NE),alcohol group of Adiantum capillus-veneris L.(ACVL.AG) and water group of Adiantum capillus-veneris L.(ACVL.WG),with 10 rats in each group. Among them 40 rats were fed for 30 days under the CMS molding condition and then were given the medicine for 15 days after successful molding. The remaining 10 rats were fed under plain condition for 45 days. The changes of pulmonary artery pressure and cardiac histomorphology were observed and the serum indexes such as C-reaction protein(CRP),erythropoietin(EPO),vascular endothelial growth factor (VEGF) and apolipoprotein A1 (Apo-A1) were detected in rats.  Results:Compared with the plain control group,the levels of PAP,CRP,EPO,VEGF in the high altitude model group,nifedipine positive control group,alcohol group of Adiantum capillus-veneris L. and water group of Adiantum capillus-veneris L. were increased (P<0.05) and level of Apo-A1 was decreased steadily (P<0.05),which suggest that hypoxia at high altitude can damage the heart tissue of rats. Compared with the high altitude model group,the levels of CRP,EPO and VEGF were decreased (P<0.05) and the level of Apo-A1 was increased (P<0.05) in the alcohol group of Adiantum capillus-veneris L. and water group of Adiantum capillus-veneris L.. At the same time,pathological changes of heart tissue were observed in CMS model rats under light microscope. The heart histomorphology was significantly improved after the intervention of the extract of Adiantum capillus-veneris L..  Conclusion:The extract of Adiantum capillus-veneris L. has protective effect on the heart of CMS rat model.