中文摘要：

由狭义相对性原理可知：在洛仑兹变换的时空坐标中，电磁场量随观察者的参考系而变，但麦克斯韦方程组的形式相同。该文从法拉第电磁感应定律和基于麦克斯韦位移电流假说的安培定律出发，推导出了在无源自由空间中时变电磁场量对以低速相对运动的不同惯性系的相对关系式，并讨论了按该相对关系变换的时变电磁场基本方程的协变性。所得结论对于理解和应用时变电磁场基本方程具有重要的指导意义。

英文摘要：

From the point of view of the principle of special relativity, it can be known that under the Lorentz transformation of space and time, the electromagnetic field vectors are different with the inertial frames, but the forms of the Maxwell equations are invariant. According to Faraday＇s law of electromagnetic induction and Ampere＇s law based on Maxwell＇s hypothesis of displacement current, the expressions for relativity of time-varying electromagnetic field in resourceless free space to inertial frames which move relatively in low speed are derived concisely. In addition, the form invariance of the basic equations of time-varying electromagnetic field based on the obtained expressions is discussed. The gained results are very important to help ones understand and apply Maxwell＇s equations of time-varying electromagnetic field.