Objective To determine the effects ofQingkailing Injection (QKL) on free calcium of synaptosomes in rats with neuroto xic brain edema (NBE) induced by L-glutamate. Methods Thirty S pragueDawley rats were randomly divided into 3 groups: ①sham control group (SHA, n=10); ②model group (MOD, n=10); ③therapy group (QKL, n=10), each rat was injected QKL (10 ml/kg, i.p.). The water content and the concentrations of sodiu m, potossium, calcium of the cerebral cortex and free calcium (［Ca2+］i) of the synaptosomes were determined at 4 hours after injecting chloride sodium o r glutamate into the right lateral ventricle. Results The level of water content 82.04%±0.8%, and the concentrations of sodium (244. 4±29.3) mmol/kg and ［Ca2+］i (327.9±33.2) nmol/L signific antly increased in MOD compared with SHA 79.93%±0.59%, (213.8±13 .0) mmol/kg, (159.6±18.6) nmol/L,P<0.01, P<0.05, P<0.01 respectively, while the concentraion of calcium in MOD (4.76± 0.74) mmol/kg significantly decreased compared with SHA (5.21±0.81) m mol/kg (P<0.05). The water content 80.13%±0.72% and the concent rations of sodium (209.4±14.7) mmol/kg and ［Ca2+］i (162.5± 17.6) nmol/L significantly decreased in QKL compared with MOD (P<0.01, 0.01, 0.01 respectively), while calcium (5.44±0.76) mmol/kg increased (P<0.05). Conclusions These findings suggest that QKL can protect against NBE, whose mechanism may be related to preventing the free calcium of the synaptosomes influx.