Objective To investigate the application value of coronary CT angiography(CCTA)and CT angiography derived fractional flow reserve(CT-FFR)in diagnosis of coronary ischemic disease(CID).Methods A total of 108 patients with coronary heart disease treated in Jinhua People's Hospital from May 2021 to June 2023 were selected as study objects.Using coronary angiography as the gold standard,the patients were divided into CID group(n=66)and non-CID group(n=42)according to myocardial fractional flow reserve.CCTA parameters[minimum lumen area(MLA),minimum lumen diameter(MLD),percentage of area stenosis(%AS),percentage of diameter stenosis(%DS)]and CT-FFR were compared between two groups.The relationship between clinical features and MLA,MLD,%AS,%DS and CT-FFR in CID group was analyzed.Receiver operating characteristic(ROC)curve was drawn to analyze the effectiveness of CCTA and CT-FFR in diagnosing CID.Results MLA,MLD and CT-FFR in CID group were significantly lower than those in non-CID group,and%AS and%DS were significantly higher than those in non-CID group(P<0.05).MLA,MLD,and CT-FFR in patients with severe calcification or stenosis were lower than those in patients with mild-to-moderate calcification or stenosis,while%AS and%DS were higher than those in patients with mild-to-moderate calcification or stenosis(P<0.05).MLA,MLD,and CT-FFR were negatively correlated with the degree of calcification and stenosis,and%AS and%DS were positively correlated with the degree of calcification and stenosis(P<0.05).The diagnostic accuracy of CT-FFR was higher than that of CCTA(86.11%vs.70.37%,χ2=7.859,P<0.05).ROC curve analysis showed that area under the curve(AUC)of CCTA and CT-FFR for diagnosing CID were 0.706 and 0.860,respectively.AUC of CT-FFR was higher than that of CCTA(Z=2.347,P<0.05).Conclusion Both CCTA and CT-FFR have certain value in diagnosis of CID,but CT-FFR is more efficient and provides more comprehensive information of myocardial ischemia.