A graphene frequency tripler (GFT) is proposed. The graphene is similar to anti-parallel diodes, which has nonlinear characteristic. In order to improve the efficiency of the GFT, the output port of the GFT uses the reflector networks to recover the power of the fundamental and fifth harmonic wave. According to the mechanism, a sample GFT is designed, fabricated, and measured. In its operation frequency of 12 GHz to 30 GHz, the minimum conversion loss of −24.2 dB can be obtained at 18 GHz when the input power is 14 dBm.