Abstract: Abstract: With the continuous improvement of modern agricultural automation technology, agricultural robots have become the new trend of agricultural machinery. As an auxiliary mobile platform of agricultural machinery, robots with feet have unique advantages compared with other mobile platforms and have been widely used in various fields of agriculture. The quadruped robot has the advantages of movement pattern of four-legged mammals and very strong adaptability and flexibility to complex terrain. Therefore, the quadruped robot has gradually become an magnet of new area. As an auxiliary mobile platform for agricultural machinery, the smooth motion posture of quadruped robot directly influence on its work performance when walking on a slope. In order to improve the stability and smoothness with load of the quadruped mobile platform while walking on the farmland, a vector control strategy of the three-dimensional slope is proposed in this paper. First of all, according to the structure, topological mode and parameters of each joint of the four-legged mobile platform, the coordinate transformation of the link of the leg is established and the kinematics is modeled. Based on the transformation relationship between the four-legged mobile platforms, the kinematic positive and inverse solutions are carried out, then the kinematic solution of the foot-end position and the leg joint angle of the four-legged mobile platform is achieved. The second, based on the kinematics model of quadruped mobile platform, the transformation equations between the angle of body and the swing angle of the leg joints on the three-dimensional slope were reduced, by analyzing the change of attitude vector on two-dimensional (pitch and roll) slope. Then, the Walk gait planning on three-dimensional slope and Trot gait planning on flat surface of the agricultural quadruped mobile platform were carried out, by using the Euler dynamic equation, SLIP theory and the stability margin theory of sub optimal support triangle. According to simulation result of slope attitude by Matlab/SimMechanics, we studied its control strategy, select pitch and roll attitude change as the limit of minimum angle. The third, the result of Matlab-adams virtual prototype simulation verify the practicability of this method about the three-dimensional attitude transformation equations and the gait planning. We can get the conclusion that the pitch and roll angle changes in the range of -2°−2°, when the mobile platform walking on the three-dimensional slope with pitch and roll are both 10°. The last, the walking experiment on three-dimensional slope was carried out. The experiment results were basically consistent with the simulation; This results verify the rationality of this three-dimensional slope attitude transformation equation and gait planning; This method not only achieve the aim of maintaining the upper platform on the level surface, but also improve the walking stability, when the quadruped mobile platform is walking on the slop; For the four-legged mobile platform load stability experiment, the static load capacity will be tested. According to the relative load error of load quality with slope changes with or without attitude control, and as an evaluation index, the results show that: The proposed attitude control strategy for slopes improves the load stability by 15.8%, 16.2% and 16.0% respectively compared with the non-attitude controller when walking on the upper and lower slopes or three-dimensional slopes. It enhanced the performance of four-legged mobile platform as the agricultural mobile . The performance of the auxiliary platform provides a reference for the design of the motion attitude control of the modern agricultural mobile platform.