This paper represents the eighth harmonic Push-Push oscillator. A both-sided MIC technology is adopted in the oscillator. The oscillator consists of a slot ring resonator, microstrip line, and two negative resistance circuit using HEMT. The microstrip line is used for the power combining circuits, This kind of oscillator has advantages such as easy circuit design, the simple circuit configuration and the miniaturization of the circuit size. The oscillator is expected to achieve millimeter wave oscillators at low cost.