Objective To explore the effect of systematic respiratory training on lung function in patients with mild to moderate traumatic brain injury. Methods A total of 60 patients with craniocerebral injury who received conservative treatment from January 2015 to June 2017 were selected. These patients were randomly divided into two groups: breathing training group for systematic breathing training and conventional treatment group for conventional rehabilitation training. Pulmonary infection, length of hospital stay, lung function determination, vital capacity, percentage of maximal ventilation, patient’s oxygen saturation, arterial partial pressure of oxygen, peak airway pressure, airway resistance, and respiratory mechanics were observed. Results The pulmonary infection rate and the length of hospital stay in the respiratory training group were 10.0% and (8.17±0.99) days, respectively, which were significantly lower than those in the conventional treatment group [33.3% and (12.67±0.99) days, respectively]; the differences between the two groups were statistically significant (P<0.05). At the same time, pulmonary function, oxygen saturation, arterial oxygen tension, and respiratory mechanics were all better in the breathing training group than those in the conventional treatment group, the differences between the two groups were statistically significant (P<0.05). Conclusion Breathing training can significantly improve the recovery of lung function in patients with mild to moderate traumatic brain injury, reduce the incidence of complications and effectively improve the prognosis.