衍射光栅可以将不同波长的光在空间上分离开，在光谱分析领域中有广泛应用.利用光栅的衍射来测量光栅常数是大学物理实验中的一个典型实验，而本文介绍的正是光栅衍射实验中的两个有趣现象：一是旋转光栅时，谱线的偏转角存在一个最小值;二是光栅旋转到一定角度时，衍射光斑会逐渐消失在视野中.论文从理论上分析解释这两种现象，并设计出两种测量光栅常数的方法，在实验上进行验证.与传统的用最小偏转角测光栅常数的方法相比，本文重点分析了由判定最小偏转角位置偏差所带来的影响，并提出了对称旋转测量的方法来进一步减小误差.

Diffraction gratings can separate the light of different wavelengths spatially，which have graduallyreplaced prisms for application in most areas of spectral analysis.Measuring the grating constant by grating diffraction is a typical experiment in the experiment of college physics.This paper introduces two interesting phenomena found during the grating diffraction experiment：(i)there is a minimum diffraction angle when rotating the grating angle，and (ii)when the grating is rotated to a certain angle，the diffracted spot will gradually disappear into the field of view.Then，we analyze and explain these two phenomena in theory，and we design two methods for measuring grating constants.Moreover，we verify these two methods in experiment.Compared with the traditional method of measuring the grating constant with the minimum deflection angle，this paper analyzes the influence of the position deviation of the minimum deflection angle，and proposes a method of symmetric rotation measurement to further reduce the error.