[Objective] To investigate the incidence of postoperative delirium and its related clinical risk factors in elderly patients with hip fracture. To explore the relationship between Mini-cog scale score and delirium. [Methods] 70 elderly patients with hip fracture underwent surgery in our hospital were included. We collected patients’preoperative serum sodium concentration, preoperative traction, preoperative non-ambulatory days, length of operation, decline in hemoglobin on the third day after surgery, morphine drug use, admitting in the intensive care unit, Charlson comorbidity index, and onset of delirium within 7 days after surgery. Each patient was administered the MMSE and Mini-cog by the primary nurse, and the duration time were documented. [Results] Twenty-eight patients (40%) developed delirium within 7 days after surgery. Preoperative non-ambulatory time was longer in delirium group than in non-delirium group (P<0.01), preoperative serum sodium concentration was lower (P=0.011), decline in hemoglobin on the third day after surgery was higher (P<0.01), and Charlson comorbidity index was higher (P=0.007). MMSE and Mini-cog scores were significantly lower in delirium group than the non-delirium group (P=0.044, 0.028). The results of single factor logistic analysis showed that the risk factors for postoperative delirium were preoperative non-ambulatory time (OR=2.139，95%CI 1.372-3.333，P=0.001), preoperative serum sodium concentration (OR=0.831，95%CI 0.722-0.956，P=0.010), Charlson comorbidity index (OR=1.598，95%CI 1.118-2.284，P=0.010), MMSE score (OR=0.949，95%CI 0.905-0.996，P=0.035) and Mini-cog score (OR=0.685，95%CI 0.498-0.942，P=0.020). To finish the Mini-Cog cost 3.9±1.6 minutes, which was significantly less than MMSE(12.1±4.8 minutes) (P<0.001). [Conclusion] The onset of postoperative delirium of elderly patients after hip fracture surgery is associated with preoperative non-ambulatory time, preoperative serum sodium concentration, Charlson comorbidity index, preoperative MMSE and Mini-cog scores. Mini-cog as a simple and effective way to assess cognitive impairment could screen high risk of delirium among elderly patients after hip fracture surgery.