A wheel leg type mobile robot with a flexible trunk is composed of the robot trunk, a front wheel leg device and a rear wheel leg device. The robot trunk is formed by connecting two isomorphic joint modules. Each joint module is composed an outer U-shaped frame, an inner U-shaped frame, an overturning steering gear, rotating shafts, a steering gear output disc, a direct-current motor, a direct-current motor output gear, a rotating gear, a bearing and a rotating disc. The overturning steering gear is fixed in the outer U-shaped frame and drives the inner U-shaped frame to be overturned up and down, and the direct-current motor output gear is meshed with the rotating gear to drive the rotating disc. The front wheel leg device comprises a steering gear box, steering gears, steering gear output discs, universal wheels and legs. The rear wheel leg device and the front wheel leg device are basically identical and only different in leg orientations, four steering gears and the steering gear box are fixedly connected through screws, and the universal wheels and the legs are respectively fixedly connected with steering gear rotating shafts. The wheel leg type mobile robot with the flexible trunk is simple in structure, can continuously move when overturned, and has high environment adapting capability.