BACKGROUND Exposure to high sustained +Gz. (head-to-foot inertial load) is known to have harmful effects on pilots body in flight. Although clinical data have shown that liver dysfunction occurs in pilots, the precise cause has not been well defined. AIM To investigate rat liver function changes in response to repeated +Gz. exposure. METHODS Ninety male. Wistar rats were randomly divided into a blank control group (BC group, n = 30), a +6 Gz/5 min stress group (6GS group, n = 30), and a +10 Gz/5min stress group (10GS group, n = 30). The 6GS and 10GS groups were exposed to +6 Gz and +10 Gz, respectively, in an animal centrifuge. The onset rate of +Gz was 0.5 G/s. The sustained time at peak +Gz was 5 min for each exposure (for 5 exposures, and 5-nun intervals between exposures for a total exposure and non-exposure time of 50 min). We assessed liver injury by measuring the portal venous flow volume, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AK), liver tissue malondialdehyde (MDA), Na - K'-ATPase, and changes in liver histology. These parameters were recorded at 0 h, 6 h, and 24 h after repeated +Gz exposures. RESULTS After repeated +Gz exposures in the 6GS and the 10GS groups, the velocity and flow signal in the portal vein (PV) were significantly decreased as compared to the BC group at 0 h after exposure. Meanwhile, we found that the PV diameter did not change significantly. However, rats in the 6GS group had a much higher portal venous flow volume than the 1.0GS group at 0 h after exposure. The 6GS group had significantly lower ALT, AST, and MDA values than the 1.0GS group 0 h and 6 h post exposure. The Na+-K+-ATPase activity in the 6GS group was significantly higher than that in the 10GS group 0 h and 6 h post exposure. Hepatocyte injury, determined pathologically, was significantly lower in the 6GS group than in the lOGS group. CONCLUSION Repeated +Gz exposures transiently cause hepatocyte injury and affect liver metabolism and morphological structure.