Objective The relationship between the percentage of the total cross-sectional area (%CSA) of small pulmonary vessels for the lung area in MSCT and pulmonary function test(PET) in chronic obstructive pulmonary disease(COPD). Methods 80 COPD patients and 40 normal subjects underwent chest MSCT scans and all clinic data were analyzed retrospectively. All COPD patientsunderwentPFT were classified into mild group (n=26), moderate group (n=27), severe group (n=27) according to PET resultsrespectively. The %CSA<5 mm2 and 5-10 mm2 for the lung area (called % CSA<5 and % CSA5-10) of small pulmonary vessels were measured with Image J image-processing program. Comparison between the COPD subgroups and control group were carriedout with ANOVA test. The relationship between %CSAand PFT results was carriedout with the Spearman rankcorrelation test. Results The % CSA<5 in mild, moderate and severe COPD group were (0.68±0.11)%, (0.56±0.12)%, (0.42±0.10)%, which were lower than that in control group (0.84±0.13)%, and the difference were statistically significant (P<0.05). The difference were statistically significant among the COPD subgroups(P<0.05). The % CSA5-10 in moderate and severe COPD group were (0.19±0.09)%, (0.18±0.06)%, which were lower than that in control and mild group [(0.32±0.14)%,(0.28±0.08)%], and the difference were statistically significant (P<0.05). %CSA<5 in COPD patients correlatedpositively with both FEV1% and FEV1/FVC(r=0.982,0.988 P=0.018,0.012), and negatively with both RV and RV/TLC%(r=-0.946,-0.962 P=0.044,0.028). %CSA5-10in COPD patients correlatedpositively with both FEV1% and FEV1/ FVC(r=0.963,0. 0.975 P=0.037,0.025), and no correlation with RV and RV/TLC%. Conclusion The measurement of %CSA<5 and %CSA5-10 in MSCT images were correlated with PFTs, and %CSA<5 was better than %CSA5-10 which may play the role in evaluating the PFTs and severity of COPD patients.