Robots with wheeled-legged morphology usually inherit the merits from both wheeled vehicles and legged machines. The hybrid structure can greatly enhance the mo-bility capabilities of locomotive robots, making these robots adaptable to a wide range of working conditions. In this paper, we specifically consider the balancing control problem of a wheeled-legged hexapedal robot. The employed robot platform has six actively articulated wheels that can be independently controlled. More precisely, each wheel of the robot is attached to a hub using the three-bar linkage mechanism, where one of the links is realized in the form of an electric linear actuator that can extend or retract to drop or lift the corresponding wheel following an arc curve, respectively. Our goal is to devise a control strategy to simultaneously command all six linear actuators such that the robot can keep stable when traversing rough terrains. To this end, we equip the robot with an IMU sensor to monitor the status of the chassis during driving the robot. By analytically establishing the kinematic relationship between the motion of the rod of the linear actuators and the angle change of the chassis, we can make the robot maintain horizontal by means of active suspension given the current tilt angle. The effectiveness of the proposed strategy is verified with both simulation and preliminary real experiments.