Abstract: When a RFID tag is attached to the metal surface, input impedance of UHF RFID tag antenna will be changed, and even it will lead to impedance mismatching with tag's chip, so a optimization design method of the UHF RFID tag antenna impedance matching for the metal surface is proposed. Firstly, adjusting the position of short-stubs of the dipole antenna roughly, basic configuration of the input impedance of the UHF RFID tag antenna will be gotten, then genetic algorithm is used to optimize length, width and position of short-stubs of the tag antenna, so accurate impedance matching between the dipole antenna and chip of RFID tag can be reached. The simulated and measured results of the designed antenna input impedance and antenna patterns indicate that the optimization design method can make the RFID tag antenna work on the metal surface regularly.