Compact and coherent source is a key component for various applications of terahertz(THz) wave. Resonant Tunneling Diode(RTD) has been considered as candidates for THz oscillators under room temperature, because it is the electronic device with the highest oscillating frequency at present. RTD THz oscillation is of great advantages of compact structure, low power consumption, room temperature work, a certain output power, easy integration, wide coverage and so on. The output power of InP-based RTD THz oscillation could reach hundreds micro-watts at around 600 GHz. Up to now, the oscillation frequency is increased up to 1.92 THz with 0.4 μW output power. The output power of RTD oscillators can be directly modulated with bias voltage. Because of this property, the RTD oscillator can be adopted as a compact and simple source for high-capacity wireless communications which is an important application of THz waves. InP-based RTD THz oscillator is attracting more and more research interest currently.