The detailed descriptions of the histological observation of the brain and thoracic ganglion mass in Chinese mitten crab, Eriocheir sinensis were reported in this study. The brain was located between the bases of two eyestalks. It consisted of protocerebrum, deutocerebrum, tritocerebrum and each part of the nerve bundles. A variety of neuropiles and 12 types of cell clusters were observed in brain sections. The thoracic ganglion mass was observed as a flat disc in shape, close to the ventral central of carapace, and with a number of outgoing nerve bundles. Different types of cell clusters could also be observed. These results not only lay the foundation for the further research of neurosecretory cells in Chinese mitten crab, but also provide reference to investigate the brains and thoracic ganglion masses in other crustaceans.