The each leg of bionic hexapod robot has three rotating joints. The torso is a 3-UrRS parallel mechanism in tripod gait. The constraint of three chains on the movement of upper platform was analyzed through the screws theory and the orthogonal product. The Degree of Freedom (DOF) of mechanism was analyzed. Actuate joints were fixed in different actuator dispositions, the constraint lines on platform acted by each branch chain were analyzed, and the Jacobian matrix of parallel mechanism was established. The Jacobian matrix simulation and verification were carried on by ADAMS. Jacobian matrix analysis of the mechanism is of important significance to analysis of achievable space, synthesis of the mechanism dimension, path planning and coordinate control.