Abstract: The theoretical research on liquid bridge experiment in the second lesson of heavenly palace classroom is conducted. Based on the symmetry and volume invariance of liquid bridge, the geometric equation of liquid bridge shape is obtained according to the principle of minimum potential energy, and the variation law of liquid bridge shape with its length and the maximum length are discussed. A characteristic parameter R describing the shape of the liquid bridge is found, and the relationship between the parameter and the internal pressure of the liquid bridge is revealed

Key words: heavenly palace classroom, liquid bridge, surface tension, surface energy, principle of minimum potential energy