A wireless communication apparatus and an antenna system therein are provided. The antenna system includes a grounding portion and an antenna body. The grounding portion includes a ground plane and a conducting element. The conducting element is perpendicular to the ground plane and is connected to the ground plane to provide a first current path. The antenna body includes a main radiating portion and a short circuit portion. The main radiating portion is parallel to the ground plane and provides a second current path. An end of the main radiating portion is electrically connected to a signal source. The short circuit portion is electrically connected between the main radiating portion and the conducting element and provides a third current path. The directions of the first current path, the second current path and the third current path are perpendicular mutually.