The different stages of the development and morphological changes of the filter and digestive oxgans in silver carp (Hypophathalmichthys moli-trix) and bighead (.Aristichthys nobilis) were observed with tissue section, gross anatomy,microscope and scanning electron microscope. At both sides of the head,the gill-rakers of these species are almost equal in numbers and the dimensions gradually decreased from outer to inner side. When the silver carp reaches the total length of 26mm, the separable gill一rakers begin to appear in 1-2 transverse bri-dges and connected with each others. TL. 85mm, they gradually appear in gill-raker's net (sieve plate).When, the bighead reaches TL. 41-99mm, they begin to differentiate board and narrow gill--raker.A lot of mucous pores are found at the gill-rakers in adult; but without at its tip, only a few at its groove in larvae and the lateral margin of gillrakers appear in model papillae. At the surface of pala-tine folds there are secondary and micro--palatine folds, and also the haste buds scattered at the top of the micropalatine folds. There are many muscle fibers in the inner side of the palatine folds, the each gill--taker's tube and outer side of supra-pharyngeal organs. The length and diameter of intestine tube ara similar in the early stage of both species. Afterward, its length is shorter and the diameter is larger in bighead. It has found. that the filter size has close relation to the gap and papillae of gill-rakers. According to the information gathered of the silver carp,TL 7.8mm the filter size is 25μ in lower limitation, and 10μ in adult. As to the bighead, the filter size is 20--30μ, throughout its ontogenesis. The feeding progress and the function of relative organs are discussed in detail.