A reconfigurable metasurface antenna (RMA) is proposed that can be used as a full polarized beam launcher to generate arbitrarily polarized radiation waves, or as a polarization detector to identify the polarization state of unknown incoming wave. It is shown that integrating Positive‐Intrinsic‐Negative (PIN) diodes and varactor diodes on the metasurface can independently control the amplitudes and phases of two orthogonal polarization components of the radiated electromagnetic (EM) waves through bias voltage, further achieving real‐time control of the polarization states. The proposed RMA can also be used as a polarization detector to identify all possible polarization states of unknown incoming waves quickly. A prototype of RMA is designed and fabricated, and the functions of arbitrary polarization generation and detection are validated by experiments, which are consistent very well with the theoretical predictions. Due to the advantages of low profile, versatility, and fast response, the proposed RMA is promising to be used in the future wireless communication, radar, and so on.