The aim is to study the neuroprotective effect and optimize the therapeutic dose and time window of picrosede II by orthogonal test in cerebral ischemic injury in rats. The forebrain ischemia models of rats were established by bilateral common carotid artery occlusion (BCCAO) methods. The successful models were randomly grouped according to orthogonal experimental design and treated by injecting picroside II intraperitonenally with different therapeutic dose at different ischemic time. The contents of aquaporins 4 (AQP4), matrix metalloproteinases 9 (MMP 9) and cyclooxygenase 2 (COX2) in brain tissue were determined by enzyme linked immunosorbent assay to evaluate the therapeutic effect of picroside II on cerebral ischemic injury. The results indicated that the best therapeutic time window and dose of picroside II in cerebral ischemic injury should be 1) ischemia 1.5 h with 20 mg/kg body weight according to the content of AQP4; 2) ischemia 2.0 h with 20 mg/kg according to the content of MMP9; and 3) ischemia 1.5 h with 20 mg/kg according to the content of COX2 inbrain tissue. It is concluded that the optimized therapeutic dose and time window is injecting picroside II peritonenally with 10 - 20 mg/kg body weight at ischemia 1.5 - 2.0 h in cerebral ischemic injury according to the principle of lowest therapeutic dose with longest time window.