Abstract: Five young male subjects wearing an anti-G suit were exposed to +G stress at four seatback angles and were tested for tracking performance on a human centrifuge of six meter radius. Some physical parameters, tracking error, output signal of side-arm controller and physiological parameters such as ECG, upper arm blood pressure and respiration were recorded. Method of complex analysis and system indentitication were used for data processing.It showed that subject's mean tracking error and psycho-physiological load increase with increase of G value and decrease of seat-back angles. Subject's tracking performance was improved by inflation of a-nti-G suit at G levels 0.3G lower than G levels at which peripheral vision loss occured. In comparing human operating dynamic parameters such as steady gain, effective delay time and frequency of tracking motion at 15 and 60 seatback angle. It was found that tracking performance was better at 60 seatback angle. Method for evaluation of human working ability and cause of change in human operator tracking performance under +G stress, were also analysed and discussed.