X射线衍射(XRD)实验是分析物质结构的重要手段，在物理学相关专业的教学中逐渐受到重视.本文对样品台高度变化Δz引起的测量误差进行了系统分析，发现样品台高度偏移Δz会使衍射峰位产生明显偏差Δ2θ，进而引起晶面间距和晶格常数的计算偏差.数据拟合结果表明Si样品晶面间距偏差Δd/d和晶格常数偏差Δa/a与Δz近似线性相关.本文结合Bragg-Brentano衍射几何，对上述实验结果进行了理论分析.本文对XRD实验精确测定晶格常数提供了参考依据，也将为相关教学工作开展提供重要参考.

X－ray diffraction ( XRD) is an important tool for analyzing the structure of substances and has been paid more and more attention in the teaching of physics － related majors． In this paper，the measurement errors caused by the variation of the sample stage height Δz are systematically analyzed． It is found that the sample stage height shift Δz causes a significant deviation in the diffraction peak position Δ2θ，which in turn causes a deviation in the calculation of the crystal interplanar spacing d and the lattice constant a． The results of the data fitting show that the deviation of Δd /d and the deviation of Δa /a for Si are approximately linear with Δz． Combined with the Bragg－Brentano diffraction geometry，we have theoretically analyzed the above experimental results． This work pro-vides a theoretical basis for the accurate determination of lattice constants in XRD experiments，and will also pro-vide an important reference for the development of related teaching work．