Abstract: The present paper deals with the caudal regicn muscle of 36 representative species of rays and skates of China,belonging to 19 genera,15 families and 4 crders.Cross section of the candal region muscle was made behind the clcaca.In general,the bundle of muscles can be divided into dorsomedian,dorsolateral,lateral,ventromedian,ventrolateral ones.In some species there are extermal lateral and external ventral bundles.The observation shows that morphological characters of muscles are closely connected with different ecological types.Four patterns and six subpatterns of caudal muscles of Chinese rays and skates are recognized,according to muscle structures in relation to body form,swimming efficiency and cther ecological factors.Based on the differences of muscle structure,a key to families of Chinese rays and skates is tentatively presented.