Objective To analyze the possible mechanism and drug treatment plan of diffuse alveolar hemorrhage induced by human granulocyte colony-stimulating factor injection, point out medication risks and provide reference for medical treatment and pharmaceutical care of such patients. Methods The abnormal lung conditions of a patient treated with human granulocyte colony-stimulating factor injection was found by clinical pharmacists, who participated in clinical diagnosis and treatment by analyzing of adverse drug reactions, optimization of medical treatment and pharmaceutical care. Results Diffuse alveolar hemorrhage was likely an adverse drug reaction caused by human granulocyte colony-stimulating factor injection. The physician discontinued the medication immediately and provided treatment such as oxygen inhalation, high-dose hormone shock, plasma exchange, etc. The patient’s oxygen saturation was improved, alveolar bleeding was decreased, and the condition was improved. Conclusion Clinical pharmacists participate in patients’ medication treatment, carry out pharmaceutical guardianship, and assist physicians in adjusting treatment plans, which could contribute to the effectiveness and safety of patient treatment.