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The paper starts from the polarization of the electromagnetic wave launched by the transmitter, develops an ionospheric heating model for a wide range of launching angles and polarizations of powerful heating radio waves. The electric field polarization is characterized by Q and ϕ, where Q characterizes the relative amplitude of the electric field components and ϕ characterizes the relative phase of the electric field components. We use similarity transformation and tensor calculation in our calculations and give the optimal polarization equation using the idea of finding the maximum value of a binary function. Combining the ionospheric background data of three widely separated locations—EISCAT (polar region), Beijing (mid-latitude), and Sanya (low latitude)—we have numerically calculated and discussed the three sites based on the heating model. The following conclusions are drawn from the calculations. The Q of the optimal polarization gradually decreases and tends to be stable when the collision frequency becomes negligible relative to the ionospheric cyclotron frequency. Q also depends on the angle between the radio wave launching angle and the magnetic inclination angle. The optimal polarization angle ϕ is generally π/2 in northern hemisphere heating experiments. With the angle between the radio wave launching angle and the magnetic inclination angle increasing from 0, the optimal polarization changes from left-handed circular polarization to left-handed elliptical polarization, and when it reaches π/2, the optimal polarization becomes east–west linear polarization. These results will provide some guidance in future experiments. [ABSTRACT FROM AUTHOR]