The invention discloses a lateral control method of the horizontal waking of an under-actuated two-foot walking robot, which has large lateral motion adjusting capacity, is not easy to fall down laterally under the condition of large and medium interference, and has good robustness. When the robot vertically stands, a vertical line passing through the centroid of the robot and the plane of the walking of the robot at the moment are interested on an intersection point; when the robot laterally swings, the centroid of the robot and the intersection point can define a straight line at each swing instant, and an defined lateral inclination angle is an included of the straight line and the vertical line; and the lateral control steps are that (1) setting a lateral inclination angle given value, (2) sampling a lateral inclination angle in real time; (3) comparing the lateral inclination angle and the lateral inclination angle given value to obtain errors, and next, carrying out fuzzy control by a fuzzy controller according to the errors e, wherein the fuzzy control process is that if an absolute value of e is less than a given threshold, the existing position of an arm is maintained to be unchanged, otherwise, the fuzzy controller controls a motor at a joint of the arm to rotate, and the motor drives the arm to swing up and down.