Through silicon vias (TSVs) are arranged to form a rectangular resonant cavity to improve performance of silicon based antenna in this paper. On the basis of fundamental theory of resonant cavity, the model of cavity made of through silicon vias is analyzed. Considering the size of millimeter- wave antenna, the three dimensions of cavity for mode TE101 is calculated. Applying it on coplanar waveguide (CPW) coupled slot antenna, a new frequency is achieved which can lead to dual bands or a wider bandwidth. And the radiation gain can be improved by 1.9dB. So the application of through silicon via on improving performances of silicon based antenna is effective enough.