Abstract: The basilisk lizard's function of walking on water is used to analyze the dynamical mechanism of a biped robot which has the same function. The movement equations of the Watt-I planar linkages are deduced by combining the movement equations of the planar four-bar mechanism and the coordinate transformation equations, in order to simulate the foot trajectories of the basilisk lizard, and the propulsion system of the biped robot walking on water is designed. The links' parameters are optimized by taking the trajectories overlap ratio as the objective function. The dynamics analysis on the robot is carried out to select the appropriate drive and transmission system. At last a real robot prototype is manufactured, and curves of the reacting force from water are measured. The experiment results show that the propulsion mechanism can generate the similar propulsion force with the force generated by basilisk lizard when it is walking on water, whose value is about 1.3 N. It is shown that the propulsion system can satisfy the function requirements of biped robots walking on water.