In order to study the fine morphologyand ultrastructure of telencephalon in zebrafish(Danio rerio)deeply, light microscope and electron microscope were adopted to observe the telencephalon of zebrafish brain.The telencephalon consists of olfactory bulbs and the cerebral hemispheres.A pair of olfactory nerves lie anterior to olfactory bulbs, and olfactory bulb connects with the cerebral hemisphere through olfactory stalk.The olfactory bulbs were composed of epithelium layer, nerve fiber layer, glomerular layer and internal cellular layer from external to internal under light microscope.Cerebral cortex covers on the cerebral hemispheres and striatum is located in the base of cerebral hemispheres.And public ventricle emerges between the cerebral cortex and the striatum.The striatum comprised nerve nuclei and nerve fibers.Nerve nuclei including dorsal olfactory nucleus, lateral olfactory nucleus, preoptic nucleus and entopeduncular nucleus, which are located in the periphery of the striatum.Nerve fibers include commissure anterior, longitudinal central olfactory tract and lateral olfactory tract.Mitral cells and synapses can be observed in the nerve fiber layer and glomerular layer of olfactory bulb under electron microscope.Besides, the astrocytes, synapses and blood-brain barrier system also arise in the cerebral hemispheres through TEM.The morphological structure of telencephalon in zebrafish is similar to those in other teleosts, but still exist individual differences in some nuclei.Thus, the results of this study can provide a theoretical reference for the establishment and application of zebrafish's neurobiological model.