This experiment was to study the effects of different dietary protein sources on gastrointestinal development in early weaning calves. Fifteen neonatal healthy Holstein calves from 2~8 weeks of age were randomly allotted to three treatments and were fed milk replacers, of which the ratios of protein from milk and plant were 80∶20, 50∶50 and 20∶80, and were labeled as S20, S50 and S80, respectively. The results showed that protein sources of milk replacers affected the ratio of gastrointestinal tract to body weight in early weaning calves, and rumen reticulum proportion was increased (P>0.05) while abomasum (P>0.05), liver and pancreas proportions were decreased (P<0.05) with the increase of plant protein. The increase of plant protein improved the development of rumen reticulum in which the rumen papilla height was higher, the shape of which showed ligule or cylinder and the color of epithelium in treatment S80 was deeper than that in other treatments, indicating that plant protein might improve digestive function of rumen in early weaned calves. Dietary protein sources affected villous morphological but did not affect the ratio of villous height to crypt depth (P>0.05), which was between 3.0～4.7 in small intestine. It was concluded that the rumen development was improved to some extent and there was not negative effects on intestinal villous by feeding plant protein diet.