Objective To investigate the effect of etomidate to intracellular free calcium (_ i ) concentration changes in response to H_ 2 O_ 2 -_ induced injury on the neuronal PC12 cells. Methods PC12 pheochromocytoma cell lines were plated in 20 mm diameter cell culture dishes and randomly divided into injury group (I group) and three etomidate groups (E_ 1 , E_ 2 and E_ 3 ) with different concentrations (3 μmol/L, 6 μmol/L and 15 μmol/L). The_ i changes were continuously measured by the confocal laser scanning microscope after incubation at 37 ℃ for 30 min in 10μmol/L Fluo_ 3 enriched media and induction by 100 μmol/L H_ 2 O_ 2 in each group from the third scanning. Results The fluorescence of 90% PC12 cells increased immediately after H_ 2 O_ 2 -induced injury(P<0.05) and had significant changes at 10 s reaching the top at 80 s in I group(P<0.01). Fluorescence of 10% PC12 cells of each E group fluctuated and decreased slightly in E_ 1 group and E_ 2 group (P<0.05) after 50 s. Conclusion Etomidat can protect neuronal PC12 cells by inhibiting_ i increase on H_2O_2-induced injury.