When a wheel-legged robot is crossing an obstacle, its dynamic model will become highly nonlinear due to the wheel-legged switching factor, but the existing linear control methods are difficult to accurately describe this nonlinear characteristic, resulting in poor control effect of the robot. Therefore, an obstacle crossing control method for wheel-legged robot with high motion performance in complex environment is proposed. On the basis of in-depth analysis of the stress conditions in the obstacle crossing process of the wheel-legged robot, the method takes the angular velocity of the motor controlling the wheel leg movement of the wheel-legged robot as the key control object, and further analyzes the gait of the wheel-legged robot during the obstacle crossing process to obtain the obstacle crossing position error of the wheel-legged robot, which is input into the fuzzy cascade PID controller. At the same time, adaptive scaling factor is introduced to optimize PID controller parameters to adapt to the nonlinear dynamic characteristics of the wheelleg robot in the obstacle crossing process, and the angular velocity adjustment of the wheelleg robot motor is dynamically generated according to the complex obstacle environment to realize the obstacle crossing control of the wheelleg robot. Experimental verification shows that this method can achieve obstacle crossing of wheellegged robots under different steps, slopes, gullies and multiple compound obstacles. In the control process, the slip rate of wheellegged robots can be less than 0.1%, the operational stability is higher than 95%, and the change trajectory of the centroid of wheellegged robots is relatively gentle, which fully proves that this method can achieve the control stability of wheellegged robots over obstacles. It can effectively promote the development of wheel-leg robot in obstacle crossing field.