Traumatic brain injury (TBI) is a global health problem, and real-time monitoring of intracranial physiological and biochemical information in patients with TBI remains a challenge. In this study, we report a flexible multimodal sensor based on polyimide, which has the potential to be implanted into the skull to measure cerebral cortical discharge, intracranial temperature, brain tissue oxygen content, sodium and potassium in cerebrospinal fluid, and intracranial pressure. In addition, this sensor has good flexibility and can be implanted into the brain smoothly. The proposed technique provides a novel insight for real-time monitoring of intracranial physiological and biochemical information and is of great significance for the diagnosis of TBI.