Abstract: With the increasing complexity of quantum-dot cellular automata (QCA) circuit, the traditional 3-input majority gate is gradually unable to meet the existing requirements. In order to reduce the logic depth and cost of QCA circuit, a 5-input majority gate is proposed, which is suitable for realizing efficient single-layer QCA circuit. Firstly, the input cells are arranged separately, and the intermediate cells are inserted to ensure the logical correctness of the 5-input majority gate. Secondly, the position of the output cell is determined according to the Coulomb force between the electrons of the cell, so as to construct a low-power 5-input majority gate. Finally, a D flip-flop is designed using the proposed majority gate. The designed flip-flop has advantages, such as low complexity and less energy consumption. The function, performance and power consumption of the proposed designs are evaluated by using the QCADesigner and QCADesigner-E tools. Compared with the previous designs, the proposed 5-input majority gate can not only reduce total energy dissipation by roughly 57% but also achieve the expected high-polarization output. The proposed flip-flop can reduce total power consumption by 78% and meanwhile the complexity, area, and delay by roughly 35%, 28%, and 28%, respectively.