In view of the current hot research topic of stability found in quadruped robots under a diagonal trot motion, an analysis has been made of the influence of the body torque on the stability of the body in motion, with a new foot end trajectory function proposed. Firstly, based on an analysis of the kinematics of the robot, a 3D model and simulation environment are established with reference to the Ubot quadruped robot, to be followed by an analysis of the body torque, thus obtaining the cause of the body turnover, i.e. the reaction torque produced by the swing of the body legs, the overturning torque produced by gravity, and the impact on the foot end in motion. On this basis, by using the lateral swinging joint motion of the robot legs to provide a torque to balance the partial reaction torque and overturning torque, a foot trajectory planning is proposed based on three-dimensional space curves. Finally, the effectiveness and validity of the proposed foot trajectory planning are verified by comparative simulation experiments.