Objective To investigate the regulatory effect of branched chain amino acids (BCAA) on the expression of apoptosis related proteins after cerebral ischemia reperfusion injury and the protective effects of BCAA on ischemic brain injury in rats.Methods 40 male SD rats were randomly divided into normal diet group (n =20) and branched chain amino acid (BCAA) group (n=20) according to the random number table,and each group was randomly divided into control group (n=6),sham operation group (n=6) and model group (n =8) which used suture method to make ischemia reperfusion model.After modeling,modified Neurological Severity Scores (mNSS) was used to access the neurological impairment degree of 2,6,24,48 and 72 h in each group.The expression of apoptosis related proteins (Cleaved,Bax/Bcl-2) after 72 h was detected by the method of immune protein imprinting (Caspase3) and compared between normal diet group and BCAA group.Results Compared with the normal diet rats,the mNSS of BCAA diet rats after modeling at 2,6,24,48,72 h decreased (11.35±2.78 vs.7.15±2.41,P=0.019;9.35±1.75 vs.5.82±1.17,P=0.002;6.11±1.16vs.4.39±1.46,P=0.048;5.87±1.32vs.3.55±1.94,P=0.036;4.98±2.24vs.2.09±1.33,P=0.022).The expression of cleaved caspase3 protein and the ratio of Bax/Bcl-2 decreased in BCAA group.Conclusion BCAA can alleviate the apoptosis of rats after ischemia and reperfusion,reduce the damage of nerve function,and has a positive protective effect on ischemic brain injury.