The invention relates to a telescopic-leg energy-saving 2D under-actuated traveling device. The telescopic-leg energy-saving 2D under-actuated traveling device comprises leg parts, a hip part, a drive device, a data acquisition device and a main control device, wherein the hip part comprises a left hip part and a right hip part, which are bilaterally symmetric to each other, the drive device comprises batteries and T-type double-end coaxial motors, the batteries are arranged inside the left hip part and the right hip part and used for powering the traveling device, the left hip part and the right hip part are connected with the leg parts through crankshaft rocking bars, each crankshaft rocking bar comprises an N-type crankshaft and a leg part rotating rocking bar, the T-type double-end coaxial motors are arranged inside the left hip part and the right hip part, stators of the T-type double-end coaxial motors are fixed in the left hip part and the right hip part, rotors of the T-type double-end coaxial motors penetrate through the outer sides of the left hip part and the right hip part to be connected with the crankshaft rocking bars, the other ends of the rotors penetrate through the inner sides of the left hip part and the right hip part to be connected with the crankshaft rocking bars in the left hip part and the right hip part so as to provide power to the traveling device. The traveling device is convenient to control and simple in structure.