Objective To investigate the effect and mechanism of pulmonary artery pressure on exercise capacity after acute high altitude exposure .Methods A total of 231 persons were recruited in this study , whose vital signs,SaO2 and physical working capacity ( PWC170 ) exercise capacity were collected .The difference between groups with normal and increased MPAP was observed .Results mean pulmonary artery pressure ( MPAP ) and right ventricle ( RV )-Tei index increased substantially after acute high altitude exposure ,while PWC170 was remarkably decreased .Furthermore,it was found that those whose MPAP increased(MPAP≥25 mmHg)had higher RV-Tei and lower PWC170(P<0.01) in acute high altitude exposure group .Correlation analysis suggested that there were different levels of correlation between MPAP, RV-Tei and PWC170(P<0.01).Conclusion After acute high altitude exposure , the increased pulmonary artery pressure is one of the main causes of lowered exercise capacity .The mechanism may be associated with the decrease of right heart functions .