Abstract: Abstract: It has been claimed by quite a few researchers that dyslexia results from magnocellular deficits in the visual system. Main evidences came from studies of visual contrast sensitivity, magnocellular suppress function and visual motion perception. The present paper reviewed these studies both in support of and in opposition to this claim. It is showed that both the advocate and the opponent for the magnocellular deficit theory could provide evidences in spatial contrast sensitivity, motion perception and magnocellular suppress function. Furthermore, the paper also cited more evidences in support of the magnocellular deficit theory from physiology studies and language reading studies, which showed the relationship between reading and magnocellular deficit and the practical value of the magnocellular system deficit theory. It was suggested that uniform criterion for experiment methods in visual contrast sensitivity research should be set up to validate the magnocellular system deficit theory and new methods to differentiated parvocellular system from magnocellular system should be developed

Key words: dyslexia, magnocellular deficit theory, contrast sensitivity