The invention relates to the technical field of diodes in microwave devices, in particular to a gunn diode and a manufacture method thereof. An epitaxial wafer of the gunn diode sequentially comprises a semiconductor insulating GaAs substrate, a heavily doped lower bottom surface n+GaAs layer, an active area n-GaAs layer, an nsGaAs layer, a GaAs intrinsic lower isolation layer, an Alx Ga1-xAs intrinsic barrier layer, a GaAs intrinsic upper isolation layer and a heavily doped upper surface n+GaAs layer from bottom to top. According to the gunn diode provided by the invention, dead areas in the active area n-GaAs layer can be effectively reduced, the conversion efficiency from direct current signals to radio frequency signals is increased, the thermal stability is improved; and output oscillation frequency and power are tuned by utilizing direct current voltage. The manufacture method of the gunn diode provided by the invention is simple, convenient and easy to realize single chip integration.