The invention relates to a portable angular momentum conservation demonstration instrument which is characterized in that a rotating disc base (2) that can rotate by a bearing (3) is fixed with two smooth metal rods (1); two spring harmonic oscillators formed by light springs (4) and metal rings (5) are sheathed on the metal rods (1); and one end of the spring oscillators can be fixed at the position of the bearing (3) of a rotating disc. The demonstration instrument utilizes the oscillation of the spring oscillators to achieve the aim of changing moment of inertia of a system, and the whole instrument has visualized principle and small volume, and is convenient for carrying, thus being very suitable for demonstration at any time; the instrument not only can be used for demonstrating angular momentum conservation law, but also the relationship between the moment of inertia and mass distribution. In addition, by changing the coefficient of stiffness of the springs and the mass of the metal rings, the instrument can be used for demonstrating the relationship between the oscillation period (frequency) of the spring harmonic oscillators and the coefficient of stiffness of the springs as well as the mass of the oscillators. In a word, the demonstration instrument has the characteristics of visualized demonstration effect, small volume, light mass, low cost and simple manufacturing technique.