Objective:To observe the signal changes of blood-oxygen-level-dependent functional MRI (BOLD-fMRI) in brain tissue after inhalation of oxygen. Methods: Fifteen volunteers,9 males and 6 females,were included in the present experiment.The fMRI was conducted using 1.5T Singna Double-gradient Super Conducting Magnetic Resonance Imaging system (GE Inc).Bold-fMRI scanning was conducted using GRE-EPI sequence and data analysis was done using SPM2 software. Meanwhile,the BOLD-fMRI T2 signal changes after 15 s and 6 min inhalation of pure oxygen were observed and compared with those after inhaling normal air.Results: No obvious activation of BOLD-fMRI was observed in the whole brain after inhaling normal air.Fifteen seconds after inhaling pure oxygen,the signal changes in the whole brain mainly manifested as the signal decrease in the gray matter,with average signal change being (-0.041±0.31)% in the gray matter and about (0.056±0.26)% in the white matter; the changes were significantly different from those of the normal air group (P<0.001). Six minutes after inhaling pure oxygen,signal changes in the whole brain mainly manifested as the signal increase in the white matter,with the average signal change being about (0.015±0.365)% in the gray matter and (0.14±0.278)% in the white matter; the changes were significantly different from those of the normal air group (P<0.001).Conclusion: Inhaling oxygen for different time periods can cause different BOLD signal changes in brain tissues. BOLD T2 signal in grey matter is decreased after short-time inhalation and is increased in white matter after long-time inhalation.