Objective To analyze risk factors of prolonged length of stay （PLOS） in oldest-old patients with hip fracture after surge-ry, and to construct a prediction model. Methods The clinical records of 487 oldest-old patients with hip fracture after surgery were analyzed retrospectively, which were divided into a modeling group (n=341) and an validation group (n=146) according to the ratio of 7 to 3, and those patients hospitalized for 8 days or more after surgery were identified as postoperative PLOS, then the univariate and multivariate logistic regression analysis were conducted to construct prediction model, and its accuracy was verified. Results Male sex, time interval from admission to operation, perioperative disturbance of consciousness, number of comorbidities, and ASA classification Ⅲ-Ⅳ were independent risk factors of postoperative PLOS in oldest-old patients with hip fracture （all P＜0.05）.The nomogram prediction model was established by employing the above-mentioned risk factors.The areas under the curve （AUC） of the modeling group and the validation group for predicting postoperative PLOS were 0.768 and 0.812 respectively, and the calibration curves of the prediction model displayed a good consistency between the two groups. Conclusion Male sex, bad basic situation, and a long interval from admission to operation are risk factors of postoperative PLOS in oldest-old patients with hip fracture, the prediction model can provide a reference for clinical decision making.