The histology, histo chemistry and ultrastructure of early development of digestive tract of phyllo soma larve ( .- . ) of Panulirus stimp soni have been studied with light microscope and electron microscope in this paper. The digestive tract can be divided into foregut, midgut and hindgut. Foregut includes mo uth, esophagus and stomach. The wall of digestive tract consists of mucous layer, connective tissue, muscular layer and outer membrane. The muco us layer, which is co vered by chitin except midgut, is generally compo sed of simple columnar epithelium and basal membrane. The chitin layer can derive the formation of toothed projection, thorn, ridge and setae, and the muscular layer which has three way s of arrangement including circular muscle, longitudinal muscle and radiant muscle has larger changes in different places of digestive tract; its outer membrane includes thin connective tissue and simple squamous epithelial cells. With the development of larval stages the structure of digestive tract becomes more and more complex. Mouthpart of phllo sonalarve is developed, it consists of a upper- lip, a pair of mandible and a pair of maxilla. The wall of esophagus protrudes into lumen and forms four ridges, that make the esophageal lumen a shape of / X0 , and there are glands in connective tissue of esophagus. The stomach forms the cardiac and pyloric stomach. The structure of cardiac stomach whose chitin layer forms a few setae and thorns is simple, only rudiment of the teeth of the gastric mill o ccurs at the fourth stages of larva; but the chitin and circular muscular layer of pyloric stomach is developed, there is gland filter that consists of comb- setaes in lumen of stomach, its structure and function of filtration become better and better with the development of larval stages, and the wall of posterior part of pyloric stomach protrudes into lumen and forms four ridges, that make this stomach lumen a shape of / 工0 . The epithelial cells of midgut which have microvilli and a large bloodsinus are distributed in connective tissue and musclar layer is thin. There are six longitudinal ridges in the hindgut who se connective tissue is crossed with radiant muscule. The observation of ultrastructure shows that mito chondria and endoplasmic reticulum are most of the organelles in the epithelial cells of wall of the digestive tract and the epithelial cells of the pyloric stomach and midgut also contain rich ribosome, and there are developed mitochondria in the muscular cell of esophageal wall. In the digestive tract at all stages of larva, the study of histochemistry show s that the chitin layer contains many polysaccharides, but the quantity of glycogen of epithelial cells of midgut is less; the protein is rich in the muscular cell while the quantity of epithelial cells of cardiac stomach and midgut do secondly; the fat granules are not observed clearly in various cells and connective tissue. The relation between the structure and function of the digestive tract of the phyllosoma larve is also studied in this paper.