Objective: to assess the relationship between high altitude de-adaptation response (HADAR) and acute high altitude response (AHAR), cardiac function injury. Methods: Cardiac function indicators were assessed for 96 men (18 - 35 years old) dep- loyed into a high altitude (3700 - 4800 m) envi- ronment requiring intense physical activity. The subjects were divided into 3 groups based on AHAR at high altitude: severe AHAR (n = 24), mild to moderate AHAR (Group B, n = 47) and non-AHAR (Group C, 25); and based on HADAR: severe HADAR (Group E, n = 19), mild to mod- erate HADAR (Group F, n = 40) and non-HADAR (Group G, n = 37) after return to lower altitude (1,500 m). Results: Cardiac function indicators were measured after 50 days at high altitude and at 12 h, 15 days, and 30 days after return to lower al- titude. Controls were 50 healthy volunteers (Group D, n = 50) at 1500 m. Significant differ- ences were observed in cardiac function indi- cators among groups A, B, C, and D. AHAR score was positively correlated with HADAR score (r = 0.863, P < 0.001). Significant differ- ences were also observed in cardiac function indicators among groups D, E, F, and G, 12 h and 15 days after return to lower altitude. There were no significant differences in cardiac function indicators among the groups, 30 days after re- turn to lower altitude, compared to group D. Conclusion: The results indicated that the severity of HADAR is associated with the severity of AHAR and cardiac injury, and prolonged recovery.