Abstract: Effect on crosswell electromagnetic signal is achieved by simulating electromagnetic wave propagation characteristic in three layered cylindrical medium. Transmitting antenna is considered as vertical magnetic dipole located at the center of infinite long cylindrical wellbore casing, three layered homogeneous cylindrical medium surrounding the hole. Electromagnetic field is denoted with magnetic hertz vector, integral expression of electromagnetic field is deduced. Finally, electromagnetic field is computed by numerical integral, and the influence of casing conductivity(material), casing thickness, and frequency on the well logging signal is analyzed.