Abstract: Neuron and glial cells of ganglion in the crab Eriocheir sinensis were studied by using optical and transmission electron microscope.Each ganglion consists of many neuron and glial cells.According to the size and shape of cell,nuclei and the distribution of chromatin,the glial cells can be distinguished into three types:astrocyte,oligodendrocyte and microglial cell.The cell membrane appears three-layered,and the cytoplasm inclusions of neuron consist of Nissl body,Golgi body,endoplasmic reticulum and mitochondrium.There are many organelles in glial cytoplasm which are similar to those in neuren cell.Astrocyte nucleus is the largest and is ellipse;oligodendrocyte nucleus is spherical;microgolal nucleus is triangle or ellipse and is the smallest one.There is relationship between the quantity of neuron cells and the ability of physiological activity of appendix,that is,the more neuron cells,the stronger the ability of appendix.