Ground mobile robots have been widely applied in many fields such as resource exploration and disaster rescue. The wheel-legged hybrid robot is capable of combining the fast speed and high stability of wheeled motion and high obstacle-negotiation performance of legged locomotion, which has high research value both in engineering technology and theoretical innovation. We analyze and compare the domestic and overseas wheel-legged hybrid robot's mechanical structure, classify the wheel-legged hybrid structure's combination mode as four types to make a list and summary. Focusing on the benefit of multi-modal motion to expand analysis, we enumerate the primary motion modeling, control, and planning strategy for the wheel-legged hybrid robot. It involves the single-legged locomotion and wheeled motion, as well as foot negotiation, deformable obstacle avoidance, and trajectory planning in wheel-legged hybrid locomotion. While making the conclusion and outlook for crucial technology in motion planning, we indicate the future development direction, research idea, and challenge for wheel-legged hybrid robots.