Abstract: For the application scenario of space microwave energy collection, a dual-port dual-band dual-circularly polarized composite microstrip antenna excited by traveling-wave microstrip line is proposed. The antenna is composed of a microstrip ring operating in the low frequency band and a microstrip disk operating in the high frequency band. The antenna is fed through the coupling of two separate orthogonal cross-slots respectively, and circular polarization is achieved using four feeders on a cascaded microstrip line that are progressively rotated by 90 degrees. The entire antenna is symmetrically constructed, and the input from two different ports can produce dual circular polarization performance. The experimental results show that the relative impedance bandwidth of S₁₁<−10 dB in 880−960 MHz band and 1.85−2.45 GHz band is 8.7% and 30%, respectively. In the 885−920 MHz frequency band and 1.86−2.43 GHz frequency band, the axial ratio is less than 3 dB, and the relative bandwidth of circular polarization is 4% and 29% respectively. The radiation pattern of the antenna is good within the operating band, with gain of 5.4 dB in the lower band and 7.7 dB in the higher band. The antenna compact design and simple processing techniques provide a novel viewpoint on the development of dual-port dual-band dual-circularly polarized antennas.