Abstract: The falling ball method is a common technique used in university physics experiment for measuring the viscosity coefficient of liquids. However，it suffers from issues，such as difficulty in ball retrieval，limitations due to the transparency of the liquid and relatively low accuracy. This improved experiment is based on the principle of conversion method in physics experiments. It involves using a pulley system to shift the velocity measurement process from inside the cylinder to the outside. Additionally，a laser rangefinder and aperture structure are introduced to measure the viscosity coefficient of castor oil at different temperatures. The experimental procedure is concise and facile，offering intuitive demonstration with high precision，particularly suitable for opaque liquids. Thereby IT bears significant potential for widespread applicability.

Key words: viscosity coefficient, conversion method, opaque liquid, laser rangefinder.