In the chapter I of the thesis is to introduce the evolution of the mobile device, including the shape and the functions. In the chapter II, we discuss the protocol of the mobile device, OTA testing system, and SAR to the human. In the chapter III, I design the grounding system and antenna for the mobile device. Finally, I measured the antenna via the OTA system to compare the test data and studied the advantage and disadvantage under Free Space and the Phantom Head. This thesis is aimed at the most suitable antenna and the grounding design for the 3G dual mode sliding mobile device. Our solution can work fine under free space and the phantom head(Talking Position). The SAR value is lower and acceptable.