D-serine is an important gliotransmitter in CNS. As an endogenous ligand for glycine-bind site in NR1 subunit of NMDA glutamate receptors, D-serine is more potent than glycine at activating the site. It is synthesized from L-serine via racemization of serine racemase, which is regulated by many factors. D-serine participates in many physiological and pathological progresses, including synaptic plasticity, sensory information transmission, neural development and neurotoxicity, and is supposed as potential therapeutic target for the treatment of nervous system disease like Alzheimer disease. Here, we provide an overview of recent findings on the mechanisms of its synthesis, degradation, release and physiological and pathological functions in CNS.