Abstract: OBJECTIVE To investigate the antihypertensive effects of metoprolol on spontaneously hypertensive rats (SHR) of cardiac β1 adrenergic receptors (β1-AR) overexpression. METHODS Twenty-four twenty-week-old male SHR were divided into the AAV/Adrb1 group, sham group, the AAV/Adrb1 + metoprolol group (AAV/Adrb1+Met) and sham+metoprolol group (Sham+Met) (n=6). Adeno-associated virus vector expressing Adrb1 (AAV/Adrb1, 2×10¹² vg·mL^-1) was utilized to transfect SHR myocardium by the pericardial cavity. RT-PCR, Western blot and immunohistochemistry were performed to measure β1-AR expression in myocardium of AAV/Adrb1 group and sham group to investigate the effect of AAV/Adrb1 on SHR of cardiac β1-AR level after 4 weeks. And metoprolol (25 mg·kg^-1·d^-1 by gavage) intervention for 4 weeks, blood pressure of AAV/Adrb1+Met and Sham+Met groups were monitored weekly to study antihypertensive effect of metoprolol on SHR of cardiac β1-AR overespression. RESULTS β1-AR expression in myocardium of AAV/Adrb1 group was significantly upregulated compared with the sham group (P<0.05). While metoprolol intervention, the SBP drop pressure amplitude of the AAV/Adrb1+Met was significantly higher compared with the Sham+Met(P<0.05). CONCLUSION It has an better antihypertensive effect on SHR of cardiac β1-AR overexpression for metoprolol, and cardiac β1-AR expression may be one of the factors that affect metoprolol individual differences.