The invention discloses a novel optically controlled microwave oscillator, including a bias resistor, first coupled microstrip circuit, second coupled microstrip circuit, output microstrip circuit, microwave field effect transistor and resonator, one end of the first coupled microstrip circuit is connected to the grid of the microwave field effect transistor, the other end of the first coupled microstrip circuit is connected to one end of the bias resistor, and the other end of the bias resistor is grounded. The drain of the microwave field effect transistor is divided into two channels, one is connected with the second coupling microstrip circuit, the other is connected with one end of the output microstrip circuit, the other end of the output microstrip circuit is used as the output end,the source of the microwave field effect transistor is grounded, and the resonator is coupled with the first coupling microstrip circuit and the second coupling microstrip circuit at the same time. The resonator is a semiconductor composite dielectric resonator, which can produce a plasma layer when the light is irradiated, so that the resonant frequency of the resonator is changed, thereby changing the working frequency of the whole microwave oscillator and realizing the control of the microwave oscillator. The structure is simple and the sensitivity is high.