Abstract: For the application requirements of satellite communication high frequency band, high efficiency and polarization mode of satellite communication, this paper designs a reflective dual-band line-circular polarization converter. In this paper, we establish equivalent circuit model based on transmission line theory, and introduce regulatory factors to make numerical corrections to the geometric parameters of the polarization converter to make the model with high accuracy. In this paper, the particle swarm optimization (PSO) method is adopted to design a reflective polarization converter which can realize dual band and bipolarization conversion function in K/Ka band satellite communication. After numerical analysis and simulation analysis concluded that the polarization converter can realize left-handed circular polarization (LHCP) in receive channel (19.2−21.2 GHz), in transmit channel (29.2−30.8 GHz) implements right-hand circularly polarization (RHCP) and reduces the axis ratio (AR) below 3 dB in the maximum incidence angle of range \Delta \theta = 45\text° \left( \theta _\min = 0\text° ,\theta _\max = 45\text° \right). In addition, compared with the full-wave electromagnetic simulation technology and machine learning method, the equivalent circuit model proposed in this paper greatly reduces the time cost and significantly improves the design efficiency of the polarization converter.