本文通过对三线摆法测量转动惯量装置进行改进，在原来三线摆测量转动惯量装置的基础上,再安装一个横梁，用来放置一个新设计的三线摆，其下圆盘用3D打印质量分布均匀的薄半球壳替代，改进后装置可用于测量球对称的刚体转动惯量，尤其是应用于测量各种体育用球的转动惯量.实验测量了半薄球壳和实心球体的转动惯量，与理论值吻合很好. 实验测量了篮球、足球、排球绕轴线的转动惯量，并且与把它们看成薄球壳的转动惯量理论值进行了比较分析. 通过实验测定一定厚度均匀的球壳的转动惯量，可计算出质量均匀分布球壳的内半径，达到很高的测量精度.改进后的测量装置可在今后的实验中广泛推广.

In this article, a device for measuring inertia moment by using a threeline pendulum method is improved. On the basis of the original device，a crossbeam is installed to place a newly designed threeline pendulum. The lower disc is replaced by a thin hemispherical shell with 3D printed uniform mass distribution. The improved device can be used to measure the inertia moment of a spherical symmetric rigid body，especially for measuring the inertia moment of various sports balls. The experimental measurement of the inertia moment of a thin semispherical shell and a solid sphere are in good agreement with the theoretical values. The inertia moments of basketball，football and volleyball around the axis are measured and compared with the theoretical values when they are considered as thin spherical shells. By measuring the inertia moment of a uniform spherical shell with a certain thickness through experiments，its inner radius can be calculated and high measurement accuracy is achieved. The improved measuring device can be widely promoted in future experiments.