Abstract: Objective: The purpose of this study based on the measurement and analysis of absolute area, relative area and the average attenuation for true and false lumen in aortic dissection for distinguishing. Methods: A retrospective analysis of May 2011, to November 2013 with acute chest pain of 65 cases of suspected aortic dissection patients, the median age was 54 years, 49 cases of men and 16 cases of women. Comply with the inclusion criteria and exclusion criteria. The patients were selected for standard aorta CTA. The graphic indicators was measured by absolute area (and calculated relative area), the average attenuation for true and false lumen. Compare the absolute area, relative area and attenuation of true and false lumen. The absolute area, relative area and attenuation of AUC were calculated by ROC. Results: The average absolute area of true lumen was (656.30±386.21) mm², the average absolute area of false lumen was (951.21 ±464.32) mm², by paired sample t test, t = 49.318, P = 0.000, the difference was statistically significant; The Average relative area of true lumen was 0.33±0.14, The Average relative area of false lumen was 0.67±0.14, by paired sample t test, t=34.235, P = 0.000, the difference was statistically significant; Average true lumen attenuation value was (234.02 ±83.53) Hu, false lumen attenuation value was (238.54 ± 87.40) Hu, by paired sample t test, t = 0.914, P = 0.361, there was no statistically significant difference; the absolute area, relative area and the attenuation of AUC was 0.846, 0.950 and 0.525, P value was 0.000, 0.000, and 0.092, respectively. Conclusion: The relative area had high sensitivity and specificity that was used to identify the true and false lumen.