To investigate the effect of Compound Sang Xian Granule on blood pressure (BP) and cardiac ultrastructure of spontaneously hypertensive rats (SHR). Methods:The treatment group gavaged with Compound Sang Xian Grannule was compared with normal control group， control group gavaged with distilled water， positive control group gavaged with indapamide. BP was measured and cardiac ultrastructure was observed at the week0， week4， week8. Results: Compared with blank control group， Compound Sang Xian Granule and Indapamide significantly decreased BP at week4 and week8. Chondriosome began to swell when SHR was 4 weeks old， after 4 weeks the mitochondrion focally aggregated， and the myofibrils and crista mitochondriales focally dissolved at week 8. In the experimental group， part of cardiac myofibrils collapsed focally， chondriosome focally aggregated at the 8th week. The change of the control group was more obvious than the experimental group. Conclusion: Compound Sang Xian Granules can control blood pressure in spontaneously hypertensive rats， and acts better than Indapamide on ultra-structure of the heart.