Objective：To investigate the value of urinary activating transcription factor 3（ATF3） and kidney injury molecule 1（Kim-1）in the early diagnosis of acute kidney injury（AKI） after cardiopulmonary bypass（CPB）heart surgery. Methods：A total of 83 patients who underwent elective CPB surgery in the Department of Cardiac Surgery of Shanghai 10th People’s Hospital from January 2018 to December 2019 were selected and divided into AKI group and non-AKI group according to KIDGO diagnostic criteria. Urine samples were collected preoperatively and 2 h，6 h，12 h，24 h，and 48 h after surgery，the levels of ATF3 and Kim-1 in urine were determined by enzyme-linked immunosorbent assay（ELISA），and［ATF3］·［Kim-1］was calculated. The area under the curve（AUC）was obtained by drawing the receiver operating curve（ROC）to evaluate the clinical value of urinary ATF3，Kim-1，and［ATF3］·［Kim-1］for early diagnosis of AKI. Results：A total of 42 patients developed AKI. Compared with the non-AKI group，urinary ATF3 was significantly increased at 6 h and 12 h postoperatively，and the AUC for the diagnosis of AKI at 12 h postoperatively was 0.691（95%CI：0.576~0.807，the sensitivity and specificity were 0.43 and 0.85 when the cutoff value was 1 216 pg/mL）. The AUC of［ATF3］·［Kim-1］combined detection was 0.712 at 6 h after surgery，reaching the highest value，and the sensitivity and specificity were 0.57 and 0.78，respectively. Conclusion：Urinary ATF3 is expressed early in the urine of patients after CPB，and can be used as a diagnostic marker for AKI after CPB in adults. The predictive value of combined use is higher than that of single test，and it is a feasible way to increase the diagnostic accuracy.