Central nervous system diseases (CNSDs) refer to a range of disorders resulting from structural or functional impairments of the brain and spinal cord, including stroke, Alzheimer’s disease (AD), Parkinson’s disease, spinal cord injury (SCI), and brain tumors. As a leading cause of disability and the second leading cause of death worldwide, CNSDs involve complex pathological mechanisms that profoundly affect patients’ physical and mental health as well as their quality of life. Therefore, identifying potential therapeutic targets and developing targeted intervention strategies for the prevention and treatment of CNSDs is of great significance. Recent studies have revealed that lactate can transmit energy between cells via the “lactate shuttle” mechanism and act as an endogenous signaling molecule, exerting diverse biological functions in CNSDs. Lactylation, a novel type of post-translational modification that uses lactate and lysine residues as substrates, plays a critical role in regulating gene transcription, immune responses, and cellular metabolism under both physiological and pathological conditions. Studies have confirmed that lactate participates in the onset and progression of CNSDs through both lactate metabolism and lactylation. In AD, lactate promotes Aβ plaque formation and impairs synaptic plasticity and cognitive function. Lactylation contributes to AD pathogenesis by regulating Aβ accumulation, Tau protein phosphorylation, neuroinflammation, pyroptosis, and ferroptosis. In ischemic stroke (IS), lactate suppresses neuroinflammation and alleviates ischemic injury. Lactylation is involved in the regulation of neuroinflammation, endothelial cell apoptosis, and neuronal ferroptosis, contributing to IS progression. In SCI, lactate promotes the phenotypic transition of astrocytes from the A1 to the A2 type, thereby mitigating neural injury. Lactylation alleviates neurological dysfunction by modulating neuroinflammation, axonal regeneration, mitochondrial function, and microglial proliferation. In glioblastoma (GBM), lactate promotes M2 polarization of microglia, facilitating tumor cell growth and dissemination. Lactylation further accelerates GBM progression by enhancing tumor cell migration, proliferation, immune evasion, and drug resistance. These findings suggest that lactate may serve as a potential therapeutic target for the prevention and treatment of CNSDs. However, its precise role in CNSDs remains unclear, and the specific mechanisms by which lactate metabolism and lactylation influence disease progression warrant further investigation. Moreover, studies have confirmed that exercise, as a key non-pharmacological intervention, holds great promise in the prevention, treatment, and rehabilitation of CNSDs. Specifically, exercise can regulate lactate metabolism and lactylation, which in turn suppresses neuroinflammation, enhances synaptic plasticity, promotes neurogenesis and angiogenesis, improves mitochondrial function in the hippocampus, and facilitates the release of neuroprotective factors, ultimately contributing to the improvement of CNSDs. This review summarizes the roles of lactate metabolism and lactylation in CNSDs, as well as the potential mechanisms by which exercise regulates lactate metabolism and lactylation to improve CNSDs, providing a theoretical basis for the benefits of exercise on brain health.