Objective:To investigate how the mental fatigue affects the human meta- cognitive ability to self- monitor overt performance during the period of 63h complete sleep deprivation.Methods:Under the complete sleep deprivation,8 healthy subjects aged 21 to 26,were selected to do meta- cognitive ability test once at every 6h during three days,and their behavioral data were collected.The specific test content is a group of serial addition tasks including six difficulty levels.Results:①Through global analysis,the study shows that the correct reaction rate of the subjects completing the tasks of different difficulty level keeps a high consistency with the subjective rating degree;②Analyzing the three calibra- tion index of the whole test,namely the correlation coefficient between the subjective rating degree and the correct reac- tion rate,the slope of the calibration curve and the correct reaction rate associated with the subjective highest certainty,we find that,regarding these three index,there are no significant difference between different tests.Conclusion:The human meta- cognitive ability to self- monitor overt performance is a relatively independent ability.If the SD duration is not be- yond 63h,this ability is almost not impaired.