对称是现代物理学中位于基础地位的重要概念. 电动力学教与学中应用对称开展分析，不仅仅有助具体问题解析，

更有助于深化对电磁场宏观性质的认识和理解. 电动力学研究对象———宏观电磁场不具有实物物质形态，故其对称性并不是

显而易见的. 本文从麦克斯韦方程组出发，采用非相对论形式的语言介绍宏观电磁场具有的普遍对称性，分析居于经典宏观

电磁场理论基础地位的规范不变性是如何引起宏观电磁场对偶性破缺，并在此基础上探讨电动力学教与学中易混淆的两个

概念———磁荷与磁单极子.

Symmetry plays great importance role in modern physics. The symmetry analysis in electrodynamics is not only useful for solving specific excises，but can also provide us profound understanding of basic concepts.In this paper，we briefly summarize the general symmetry properties of electromagnetic fields in its non-relativity form. We address that gauge invariance is the fundamental symmetry classic electromagnetic field and governs the electromagnetic interaction. The broken of duality in electromagnetic field is an example of this governance. Based on these understanding，two confusing concepts，that magnetic charge and magnetic monopole，are further discussed.