Abstract: in this dissertation，the principle of FEM in EM was discussed，then athree-layered pavement were analyzed with 4-noded isoparametric elements．Then，corresponding FEM programs are compiled in Foman90．So a forward model was built up to describe the transmitting of electromagnetic in the radar and pavements,according to the system identification method.Compared with the methods of finite difference or FFT，the results are more precise and effective，which are more easily applied in projects．

Key words: GPR, electromagnetic FEM, isoparametric elements, forward model

摘要： 系统阐述了电磁场有限单元法的基本原理，然后采用四节点等参单元分别对三层路面系统进行了静态场和 时变场的有限元分析，初步建立了路用探地雷达GPR电磁波在三层路面中传播的正演模型，同实测波形相比，模拟 效果较好，并用Fortran90语言编制了相应的三维、二维有限元程序，具有较好的可读性和可移植性．

关键词: 路用探地雷达, 电磁场有限元, 等参单元, 正演模型