Objective：To investigate the effect of hypoxia on the activity of Na+K+ATPase(Na pump) and to understand the distinct functions of high and lowaffinity Na pump during hypoxia of cortical neurons. Methods: Hypoxic condition was mimicked by perfusing cortical slices or culturing cortical neurons with low oxygen solution. Sodium pump current and membrane current of neurons from cortical slices were measured by patchclamp technique in the whole cell mode and the intracellular Ca2+ concentration (\[Ca2+\]i) in cultured cortical neurons was examined by video based motion edge detection system. Changes of Na pump current induced by hypoxia were also examined 4 min after hypoxia in the neurons of cortical slices. Changes of membrane current and \[Ca2+\]i were determined 0, 2, 4, 6, 8 and 10 min after hypoxia with or without Ouabain (Oua, inhibitor of sodium pump). Results: Total sodium pump current were significantly decreased 4 min after hypoxia (\[0.265±0.068\] pA/pF vs \[0.160±0.046\] pA/pF, P<0.01). Membrane current and \[Ca2+\]i were increased in a timedependent manner 10 min after hypoxia (r=0.9803 and r=0.9734, P< 0.01). The effect of hypoxia on membrane current was abolished by tetrodotoxin(TTX,1 μmol/L, a blocker of sodium channel). Oua at 10 μmol/L significantly promoted the hypoxiainduced increase of membrane current and \[Ca2+\]i through inhibiting lowaffinity sodium pump (P<0.05 or 0.01), and Oua at 10 nmol/L significantly depressed the increase of membrane current and \[Ca2+\]i through inhibiting highaffinity sodium pump (P<0.05 or 0.01). Conclusion: Change of sodium pump activity is involved in hypoxic injury in rat cortical neurons. Highaffinity sodium pump is related to the protection of hypoxic injury and lowaffinity sodium pump is related to the hypoxic injury.