Objective To explore the features of polymorphism in ADRA2A gene phenotypes and their relationship to oxygen endurance in the Han servicemen in PLA.Methods One hundred and eight healthy recruits of Han ethnic were subjected to a 5000-meter race program for 18 weeks,and then the tests were done after a 5000-meter race.The ADRA2A allelic variant and genotype were analyzed by polymerase chain reaction and sequencing,and the features of polymorphism in three sites,G6412C,T6623A and C6645C,were determined with biochemical technique.The relationship between the results after the 5000-meter race,and the polymorphism of ADRA2A was then analyzed.Results The genotype distribution at all the three locations was consistent with the Hardy-Weinberg equilibrium.The genotype frequency in T6623A of A/G(50%)was higher than that of G/G(26%)and A/A(24%).The allele frequency of A(51%)was higher than that of G(49%).The time for completing 5000-meter running was significantly longer in recruits carrying A/G(20.95?0.82min)than those carrying A/A(18.97?0.65min,P0.05).There was no significant association between the oxygen endurance capacity and the polymorphism of G6412C and C6645C.Conclusion The T6623A of ADRA2A was the ideal gene marker for predicting endurance capacity,but G6412C and C6645C polymorphism is not ideal gene marker for oxygen endurance.