Using the falling-sphere method to measure the liquid viscosity coefficient is a basic experiment in college physics, which has attracted many attentions.The uncertainty of some measurement data in the experiment always exists,such as whether the initial velocity of the ball is zero, whether the measurement of the falling time is accurate, how to ensure the falling collimation,etc.,leading to some errors of the experimental results.Based on the possible error analysis in the experiment and the existing laser technology, we have made some improvements to the experimental instrument for measuring the liquid viscosity coefficient by the falling. sphere method, which greatly reduces the operation difficulty of the experiment.The results show that the improved experimental instrument can effectively reduce the experimental error and provide a feasible scheme for the accurate measurement of the liquid viscosity coefficient by the falling-sphere method.