In recent years, microwave heating has been widely used in various fields due to its high efficiency and internal heating. However, the uniformity of microwave heating limits the development of its large-scale industrial application. High uniformity and high efficiency are the focus of microwave heating research. Low efficiency will cause the waste of energy and non-uniform heating will lead to poor heating quality and even thermal runaway. In this paper, a method of frequency-selected heating with dual-port is proposed and the power is fed by two orthogonal polarized antennas in the cavity. Then, the heating efficiency of each frequency point and the influence of different frequencies on the heating effect are analyzed by using sweep frequency. Finally, frequency-selected heating is carried out on the frequency point with high efficiency, so as to improve the heating uniformity under the premise of maintaining high heating efficiency.