Objective To clarify the position,figure and connections with adjacencies in the pallial thickening(Pth),and provide essential parameters for its function study. Methods The coronal serial sections of 60?m thickness in gekko gecko brain were made by cryo-microtome,and Nissl staining was used.Pictures were taken in each coronal section containing the Pth and the size of Pth in each section was measured.One of them was chosen for the three-dimensional reconstruction.3D MAX was used as the tool software to rebuild the nucleus. Results 1.The Pth was located in the rostral part of the telencephalon,the lateral part of anterior dorsal ventricular ridge,the medial part of the lateral cortex and the ventral part of the dorsal cortex.The length of Pth from the rostral to the caudal end was(912.67?110.96)?m(n=10),the cubage of Pth was about(0.1430?0.0414)?m~3(n=10).2.The Pth could be divided into four segments,the anterior,the middle,the posterior and the terminal segments from the rostral to the caudal end.In the posterior segment,its dorsoventral axis was the longest,and could be divided into two parts: the dorsal and the ventral parts.The boundary of the two parts was clear.Conclusion The Pth is a long,narrow and flat structure;its rostrocaudal axis is longer than its dorsoventral axis,and its dorsal edge is smoother than its ventral edge.In the Pth,its caudal region is larger than its rostral region,and the posterior segment in the caudal region is divided into the dorsal and the ventral cell populations.