Endocannabinoids（ECS）have been implicated in a growing number of physiological functions including pain modula-tion through acting at CB1 receptors in the central and peripheral nervous system. This review summarizes the biology of endocannabinoids system and its involvement in chronic pain and stress-induced analgesia （SIA） , and the behavioral, neurophysiological and neuroanatomical evidence of cannabinoids modulating pain.