In this article, the development of a high-efficiency power amplifier (PA) with the inverse class-F configuration and a novel 3/4 spiral defected ground structure (DGS) is presented. The proposed DGS structure has improved rejection characteristic and its resonance frequencies are more convenient to adjust than conventional symmetric and asymmetric spiral structure. The electromagnetic-simulated result shows that the proposed circuit has improved harmonic control performance with simplified structure and less return loss than the conventional microstrip harmonic control circuit. The 3/4 spiral harmonics control circuit (HCC) can be modeled by three parallel RLC resonators. Using the proposed structure a high-performance harmonic control circuit is designed for implementing an inverse class-F PA. For comparison, two inverse class-F PAs operating at 2.4 GHz have been implemented by the microstrip HCC and the proposed HCC, respectively. According to the experiment results, the size of the proposed inverse class-F PA is reduced by 20%, the power-added efficiency and the gain are increased by 4.8% and 1.5 dB, respectively.