文章逐个分析计算了单摆的摆角、摆球的自转、摆线质量、空气浮力以及空气阻力对于单摆周期的影响，以 1 m 长5°小幅单摆为例，得到这 5 种因素带来的系统相对误差分别为+ 0. 45‰、+ 0. 02‰、- 0. 45‰、+ 0. 07‰、- 0. 14‰，合计仅为-0.05‰，即这 5种误差因素几乎相互抵消，小幅单摆实验在理论上的系统误差极小.文章给出了较为详细的推理、计算和分析过程，尤其空气阻力矩的推理过程以及图、表等，意在提供较为完整和准确的认识.文末，针对人们在空气阻力认识上可能存在的某些不足，文章给出了几点必要的说明.

This paper analyzes and calculates the influence of the pendulum angle，the rotation of

the ball，the mass of the suspension line，the air buoyancy and the air resistance on the period of

the pendulum one by one. Tak- ing a 1 m length and 5° swing angle small amplitude pendulum as an

example，the relative errors of the five factors are

+0.45‰，+0.02‰，-0.45‰，+0.07‰，-0.14‰，respectively，and the total is only -0.05‰，which means that the

five error factors almost cancel each other，and the systematic error of the small

pendulum experiment is very small in theory. This paper gives a more detailed

reasoning，calculation and analysis process，especially the reasoning process of air resistance

moment，as well as charts and tables，for providing a more complete and accu- rate

understanding. Finally，some necessary explanations are given in view of some possible deficiencies

in people's understanding of air resistance.