Abstract: In order to develop a new climbing snake robot(CSR) that has rather great advantages on vertical outer climbing,this paper presents a P-R(pitch-roll)module,and with a simple structure and the function of universal joint,the module is easier to control.Compared with the traditional connection ways such as parallel connection and orthogonal connection,a snake robot based on this module can adhere to the outer surface of the climbed object more easily and flexibly.Static balance mechanism of the basic poses is analyzed for the P-R-module-based CSR when it climbs a tree,and functional realationship of the related parameters is gained,providing a theoretical evidence for developing CSR prototypes and choosing climbed objects.Finally,effectiveness of the P-R module and rationality of the related analysis are validated with CSR prototype experiments