Abstract: Objective: Combining Doppler echocardiography, the comparison analysis of chest CT in the classification of pulmonary arterial hypertension(PAH) in chronic obstructive pulmonary diseases(COPD). Methods: Retrospective analysis of 100 diagnosed cases whose chest CT scan's materials by Doppler echocardiography with classification of PAH in COPD, measuring the main pulmonary artery diameter(MPAD), the right pulmonary artery diameter(RPAD) and the left pulmonary artery diameter(LPAD) which are showed on the chest CT, comparing with the above chest CT scan data of 30 cases of COPD patients without PAH, to analyze their relationaships with the classification of pulmonary arterial hypertension and to do some statistical analysis. Results: Among 100 cases of PAH, 57 patients were diagnosed as mild PAH, 27 patients were diagnosed as moderate PAH, 16 patients were diagnosed as severe PAH by Doppler echocardiography. According to three groups patients of PAH above, the MPAD which were measured in the computed tomography can be obtained by analysis of variance among the three statistically significant differences. Drawing a parallel between the two, we can find that, there are some statistical differences between the MPAD of mild PAH and moderate PAH(P = 0.017). There are statistical differences between the MPAD of mild PAH group and severe PAH group(P = 0.000). There are also statistical differences between the MPAD of moderate PAH group and severe PAH group(P = 0.031), and the data of MPAD in the mild PAH group < the moderate PAH group < the severe PAH group. The data of mild PAH group's MPAD is(29.71 ±3.57) mm, and the best diagnostic threshold is 29.11 mm; The data of moderate PAH group's MPAD is(31.77 ±3.44) mm, and the best diagnostic threshold is 30.53 mm; the data of severe PAH group's MPAD is(34.28 ±4.14) mm, and the best diagnostic threshold is 32.00 mm. Conclusion: There is some diagnostic value in the classification of PAH in COPD through measuring MPAD by chest computed tomography scanning.