Abstract: In order to solve the problem of heating non-uniformity in microwave heating, mechanical rotation methods such as mode stirrers and rotating turntables are proposed to change the electric field distribution in heated objects to improve the heating u-niformity. However, the mechanical rotation method often makes the simulation calculation difficult and increases the complexity of the microwave system. Therefore, a switchable frequency selective surface with a working frequency of 2. 45 GHz for microwave heating is proposed in this paper. By adjusting the switching state of the PIN diode, the electric field distribution can be changed. Moreover, the frequency selective surface in different states are combined in time and heat objects, which can significantly improve the heating uniformity and efficiency. The results show that the transfer coefficients of the frequency selective surface in the on and off states are -32. 10 dB and -0. 16 dB respectively, the heating uniformity and heating efficiency can be improved by 43% and by 42% respectively. It is expected to be widely used in industrial fields.