Objective To explore the prognostic factors of hospital mortality for unplanned re-exploration after cardiovascular surgery. Methods We retrospectively analyzed the data of 100 patients who underwent unplanned re-exploration after cardiovascular surgery in our hospital between May 2010 and May 2020. There were 77 males and 23 females, aged (55.1±15.2) years. Demographic characteristics, operation information, perioperative complications were collected to set up a database. The patients were divided into survival group and non-survival group according to hospital mortality. Logistic regression was used for multivariable analysis to explore the prognostic factors of hospital mortality. These statistically significant indicators were selected for drawing the receiver operating characteristic curve of the evaluation model, calculating the area under the curve(AUC) and evaluating the effectiveness of the new model with Hosmer-Lemeshow C-statistic. Results Hospital mortality was 26.0% (26/100). Multivariate logistics regression revealed that the operation time of unplanned re-exploration, the worst blood creatinine within 48h before the re-exploration, the worst lactate within 24h after the re-exploration, cardiac insufficiency, respiratory insufficiency, and acute kidney injury were independent prognostic factors (p<0.05). The AUC of the new assessment model constituted by these prognostic factors was 0.910, and the Hosmer-Lemeshow C-statistic was 4.153 (P= 0.762). Conclusions The operation time of unplanned re-exploration, the worst blood creatinine value within 48h before the re-exploration, the worst lactate value within 24h after the re-exploration, cardiac insufficiency, respiratory insufficiency, and acute kidney injury were independent prognostic factors of hospital mortality for unplanned re-exploratio after cardiovascular surgery.