In order to acclimatize amphibious bio-crab robot to the amphibious environment better, a series-parallel structure of amphibious bio-crab robot is proposed, then we designed an amphibious bio-crab robot which use the modular worm and worm wheel transmission mechanism to achieve the transmission of the leg joint. A single leg and overall walking simulation model of amphibious bio-crab robot was established, and then carried out a kinematics and dynamics simulation. Finally, through the experiment we got the kinematics parameters and characteristics of amphibious bio-crab robot, which verify the correctness of its structure design, dual four-legged gait planning feasibility and the necessary of a buffer module for physical prototype. The research also provided a viable technical solution to the physical prototype development.