In this paper, the 8th harmonic Push-Push oscillator is successfully presented. The Push-Push principle and the excellent harmonic coherency in a microwave resonator are effectively utilized. The proposed oscillator consists of two sub-circuits, a microstrip ring resonator and an output circuit. The concept of the simplified structure harmonic oscillator (SSHO) is adopted in the proposed oscillator. The microstrip ring resonator plays two roles of the common resonator and the power combiner circuit. This kind of Push-Push oscillator has practical advantages of the easy circuit design due to the simple circuit configuration and the miniaturization of the circuit size. Using the Push-Push principle and the effective circuit configuration of the output circuit, the desired 8th harmonic signal is effectively enhanced. This Push-Push oscillator achieves good millimeter-wave oscillation in V band using inexpensively available X band HEMTs. The estimated output power of -6dBm at the frequency of 51GHz is obtained with the phase noise of -93dBc/Hz at the offset frequency of 1MHz.