Abstract: A circularly polarized stacked microstrip antenna array with the application of sequentially rotated feeding technique is proposed in this paper. Stub-tuning method to optimize the impedance bandwidth is discussed and the sequentially rotated feeding technique is used to build a two element microstrip antenna array. The corresponding array is fabricated and measured. The measured results agree well with the simulation, which indicates that the stacked configuration can effectively enhance the impedance bandwidth and the gain of the microstrip antenna, while the sequentially rotated feeding technique can improve the circularly polarized purity.