The radiowave polarization plane rotation is caused by the ionospheric dispersion and the double refraction. Begin with the ionosphere refraction index, the formula of radiaowave polarization plane rotation angle is derived in this paper. Using the measured electron density, magnetic induction intensity module of geomagnetic field, and magnetic obliquity profiles, the radiaowave polarization plane rotation angle is simulated for fixed height carrier under different angles between antenna side-view and earth normal, different regions, different frequency bands, different time slots, and different solar activity cases, which is described by column diagraphs and tables. The simulation results and the rules and properties of radiowave polarization plane rotation angle are analyzed and summarized in its seasonal, temporal, regional, frequency-domain aspects. (1) The rotation angle will decrease as the frequency arises, and will increase as the angle between antenna side-view and earth normal arises. (2) The rotation angle will increase as the sun polar activity arises, larger in the day and smaller at night. (3) At night, the rotation angle in summer is the largest and in winter is the smallest as in high and middle latitude, larger in spring and autumn and smaller in summer and winter as in low latitude. (4) In the day, the rotation angle in winter and spring is larger that in summer and autumn as in high latitude, larger in spring and autumn and smaller in summer and autumn.