Abstract: The (1−x)(K_0.5Na_0.5)NbO₃-xCa(Al_0.5Nb_0.5)O₃ (KNN-xCAN, 0.02 ≤ x ≤ 0.08) perovskite ceramics were prepared by solid phase synthesis method. With the increase of CAN doping content, the phase structure of ceramic samples changes to the symmetric structure, the ferroelectric state transforms from the normal ferroelectric to the relaxor ferroelectric state, and the grain size gradually decreases. The increase of dielectric constant and dielectric loss caused by illumination. The sample at x = 0.03 shows significant photodielectric response, and its dielectric tunability of 663% can be obtained at 365 nm ultraviolet light and test frequency of 80 Hz. With the increase of test frequency, the dielectric tunability decreases rapidly and remains at about 6% after 100 kHz. When the light source is switched, an obvious capacitive switching characteristics can be observed, and is reversible. These research provide experimental basis for the development of new non-contact optical capacitor and optical switch based on KNN ceramics.