For the phenomenon that the distribution of magnetic field intensity caused by antenna coil is non-uniform, this article puts forward a solution to enhance the local antenna's magnetic field intensity. First of all, this article explains the skin effect of high frequency magnetic field from the theory. Then, based on the skin effect of high frequency magnetic field, we add a gap magnetic metal core in the central coil in order to enhance the magnetic field strength. Finally, the influence of the different opening Angle of the gaps magnetic core on the magnetic field strength of loop antenna is studied by using 3D electromagnetic simulation software Ansoft HFSS and the MATLAB software, to find out the optimal design scheme of gaps. This has a certain reference value for the actual design of the antenna in13.56 MHz RFID reader systems.