Abstract： Objective To correlate dynamic parameters at contrast enhanced CT and interstitial fibrosis grade of non-small cell lung cancer (NSCLC). Methods Twenty-nine patients with NSCLC were evaluated by multi-slice CT. Images were obtained before and at 20,30,45,60,75,90,120,180,300,540,720,900 and 1200 s after the injection of contrast media, which was administered at a rate of 4 ml/s for a total of 420 mg I/kg body weight. Washout parameters were calculated. Lung cancer specimens were stained with hematoxylin-eosin stain and collagen and elastica double stain. Spearman test was made to analyze correlation between dynamic parameters and interstitial fibrosis grade of tumor. Results Twentynine NSCLC demonstrated washout at 20 min 12. 1 (0. 32-58.0 ) HU, washout ratio at 20 minutes 15.3% (0. 3%-39.2% ), slope of washout at 20 minutes 0. 0152 %/s ( 0. 0007%/s-0. 0561%/s ).Interstitial fibrosis of 29 lesions was graded as grade Ⅰ (10), grade Ⅱ (14) and grade Ⅲ (5). There were significant correlation between washout at 20 min ( r = - 0. 402, P ＜ 0. 05 ), washout ratio at 20 min ( r =-0.372,P＜0.05), slope of washout ratio (r = -0.459,P ＜0.05) and interstitial fibrosis grade in tumors. Conclusion NSCLC washout features at dynamic multi-detector CT correlates with interstitial fibrosis in the tumor.