Abstract: Pain has been identified to impact mental processes, like cognition, emotion, etc. Pain may disturb individual’s selective or persistent attention, and even damage one’s memory function. Long-term pain can also cause negative emotions, such as anxiety and depression. Two main theories of pain mechanism, the Gate Control Theory and the Neuromatrix Theory, explained the interaction between pain and mental processes at spinal cord level and at brain level respectively. The theories which explained coding mechanisms of pain included Specificity Theory, Pattern Theory and “Cell Assemblies” Theory. Future studies should pay attention to the differences between laboratory and clinical researches, and distinguish specific mechanisms of acute pain and chronic pain, and then demonstrate the rationality of these pain theories.

Key words: pain, pain mechanism, gate control theory, neuromatrix theory, coding mechanism