Snake robots play a crucial role in search,rescue operations and fire-fighting where it may either be too narrow or to dangerous for personnel to operate. properties such as high terrainability, redundancy, and the possibility of complete sealing of the body of the robot, make polybots very interesting for practical applications and hence as a research topic. during the last ten to fifteen years, the published literature on snake robots has increased vastly. however, no through review of the theory presented in this period regarding structure and locomotion of snake robots in field of agriculture(irrigation) has been found.the purpose of this paper is to give such a review. the choice of modeling method is linked to robotic design characteristics and locomotion approach of nasa’s ames research center. different approaches of biologically inspired locomotion and mechantronics structure of it is dicussed below.