This work presents a controller designed for position-controlled quadrupedal dynamic locomotion,aiming at simple and robust trotting control. The controller takes the torso attitude angles and velocities into planning foot trajectories. Firstly design of the servo motor actuated quadruped robot is introduced and the kinematic equations are deduced. Then a scheme is presented for controlling the robot torso attitude based on the virtual leg model. Furthermore,it demonstrates the design of the controller which enables the robot to have a wide range of trotting gaits and omni-directional motions. Finally,results of robust trotting in various speeds,path tracking and push recovery in simulation are reported,and results of trotting on real quadruped robots will be studied. This work presents a controller designed for position-controlled quadrupedal dynamic locomotion, aiming at simple and robust trotting control. The design takes the torso attitude angles and velocities into planning foot trajectories. The design of the servo motor actuated quadruped robot is introduced and the kinematic The equations are deduced. Then demonstrates the design of the controller which enables the robot to have a wide range of trotting gaits and omni-directional motions. Finally. , results of robust trotting in various speeds, path tracking and push recovery in simulation are reported, and results of trotting on real quadruped robots will be studied.