Abstract： Objective To investigate the difference of + Gz tolerance between male and female student pilots by testing the forces developed by respiratory and leg muscles,and to verify the G tolerance test by means of anti-G training apparatus. Methods Thirty-two female and thirty male student pilots volunteered for this study.The vertical heart-to-eye distance,maximum expiration pressure,maximum inspiration pressure and forces developed by leg muscles,systolic blood pressure when performing HP and PHP maneuver were measured.The + Gz tolerance was reckoned by an empirical formula when volunteers riding on anti-G training apparatus with the performance of straining maneuver and anti-G suit. Results The vertical heart-to-eye distance,maximum expiration pressure,maximum inspiration pressure and forces developed by leg muscles of male student pilots were significantly greater than those of the females (t=4.852～6.762,P＜0.01).The G tolerance of male students in performing PHP maneuver was greater than that of the females (t=2.226,P=0.034).There was no significant difference in G tolerance when performing HP maneuver between female and male student pilots (P =0.185). Conclusion ① The respiratory and leg muscles of female student pilots are not as strong as male student pilots'.② Female student pilots may beneficially gain G tolerance due to their shorter heart-to-eye distance,but they could reach relative lower systolic blood pressure when performing HP maneuver.Such resulted effects maybe the important reason of causing female' s inapparent G tolerance improvement comparing to the male' s.Because of their weaker respiratory muscles,the female students do not accommodate themselves to PBG (positive pressure breathing for G) and show poorer G tolerance as they performing PHP maneuver with PBG.③ The blood pressure measurement when performing AGSM (anti-G straining maneuver) need to be improved for getting better success rate and accurateness.