Objective : The present study aimed to investigate the clinical characteristics of electrolyte imbalance in patients with moderate to severe traumatic brain injury (TBI) who underwent craniotomy and its influence on prognosis. Methods : A total of 156 patients with moderate to severe TBI were prospectively collected from June 2019 to June 2021. All patients underwent craniotomy and intracranial pressure (ICP) monitoring. We aimed to explore the clinical characteristics of electrolyte disturbance and to analyze the influence of electrolyte disturbance on prognosis. Results : A total of 156 patients with moderate and severe TBI were included. There were 57 cases of hypernatremia, accounting for 36.538%, with the average level of 155.788±7.686 mmol/L, which occurred 2.2±0.3 days after injury. There were 25 cases of hyponatremia, accounting for 16.026%, with the average level of 131.204±3.708 mmol/L, which occurred 10.2±3.3 days after injury. There were three cases of hyperkalemia, accounting for 1.923%, with the average level of 7.140±1.297 mmol/L, which occurred 5.3±0.2 days after injury. There were 75 cases of hypokalemia, accounting for 48.077%, with the average level of 3.071±0.302 mmol/L, which occurred 1.8±0.6 days after injury. There were 105 cases of hypocalcemia, accounting for 67.308%, with the average level of 1.846±0.104 mmol/L, which occurred 1.6±0.2 days after injury. There were 17 cases of hypermagnesemia, accounting for 10.897%, with the average level of 1.213±0.426 mmol/L, which occurred 1.8±0.5 days after injury. There were 99 cases of hypomagnesemia, accounting for 63.462%, with the average level of 0.652±0.061 mmol/L, which occurred 1.3±0.4 days after injury. Univariate regression analysis revealed that age, Glasgow coma scale (GCS) score at admission, pupil changes, ICP, hypernatremia, hypocalcemia, hypernatremia combined with hypocalcemia, epilepsy, cerebral infarction, severe hypoproteinemia were statistically abnormal (p<0.05), while gender, hyponatremia, potassium, magnesium, intracranial infection, pneumonia, allogeneic blood transfusion, hypertension, diabetes, abnormal liver function, and abnormal renal function were not statistically significant (p>0.05). After adjusting gender, age, GCS, pupil changes, ICP, epilepsy, cerebral infarction, severe hypoproteinemia, multivariate logistic regression analysis revealed that hypernatremia or hypocalcemia was not statistically significant, while hypernatremia combined with hypocalcemia was statistically significant (p<0.05). Conclusion : The incidence of hypocalcemia was the highest, followed by hypomagnesemia, hypokalemia, hypernatremia, hyponatremia and hypermagnesemia. Hypocalcemia, hypomagnesemia, and hypokalemia generally occurred in the early post-TBI period, hypernatremia occurred in the peak period of ICP, and hyponatremia mostly occurred in the late period after decreased ICP. Hypernatremia combined with hypocalcemia was associated with prognosis.