Abstract: Transmission characteristics of signal crossing the boundary of different tissues in human body are studied through calculating the incidence of electromagnetic wave at the tissue boundaries. Reflection coefficient, transmission coefficient and the expression of electromagnetic field are deduced from the boundary conditions firstly when the uniform plane electromagnetic wave incidence to the single layer and multi-layer mediums. Then the human arm is taken as a research object, and the fourth-order Cole-Cole model issued to obtain the dielectric parameters of body tissues in 10 Hz-100 GHz. After that, the maximum incident angle, reflection coefficient, transmission coefficient and average energy flux density on the boundaries are calculated when electromagnetic wave incidence to 1-layer, 2-layer and 3-layer tissues. The results show that electromagnetic wave is propagating through the multi-layer tissues mainly with the vertical incidence, the reflection coefficient on the boundary of skin and air is larger than any other tissues, the energy of electromagnetic wave is difficult to be transmitted inside and outside the body with a frequency less than 1 MHz or larger than 10 GHz, the average energy flux density of electromagnetic wave presents band-pass characteristic with frequency, and the bandwidth and center frequency are related to the implantation position of device. Finally, a finite element simulation model of vertical incidence to the 3-layer human body tissues is built by using COMSOL Multiphysics. The differences between the simulation results and calculation results are less than 0.000 08, which verify the accuracy of the theoretical deduction and calculation.