To acquire more environmental information for planning further tasks, the snake-like robot has to raise its head to observe the situation at a high position due to its low-height stature, which resembles the head-raising motion of the natural snake. In this paper, the motion of snake-like robot raising head is realized by improving the serpentine input function, and two methods of head raising motion were proposed. The dynamic model of head-raising motion is built to analyze the input torque of each joint for getting optimal dynamic performance. Comparative results of two methods of head-raising motion are shown by computer simulations, and the stability of motion is analyzed by means of ZMP (zero moment point) method. The experimental results show the validity of the presented methods