The general RFID theory and principal of operations are reviewed, and the conductivities of the various electro-threads are analyzed. Based on the analyzed data, an embroidery tag antenna using the electro-thread is designed with the popular English character shape A. The embroidery RFID tag is easy to be embedded on a cloth as a wearable antenna. The embroidery tag is easy to be applied to general clothes. The characteristics and the reading range patterns of the tag antenna are measured. The reading distance of the A shape embroidery tag antenna is 1.2 meter at the maximum range.