WiFi Direct (WFD) supported by Android has been widely used in device-to-device (D2D) communications. Compared with Bluetooth, WFD has advantages in data transmission rate and connection distance. At the same time, WFD can quickly create a connection than WiFi HotSpot. Therefore, it is widely used to form D2D communication networks and support edge computing, traffic offloading, mobile crowdsourcing, and other studies. However, it brings high energy consumption simultaneously, which is still a major concern for battery-constrained devices. Existing studies pay more attention to measuring and optimizing the performance of WFD-based networks, while few studies focus on the energy consumption. In this study, an energy-saving mechanism for the WFD based on power control is proposed, which makes a supplement to the default energy-saving mechanism of WFD. First of all, this study constructs a WFD-based communication group and a measurement analysis of the default energy-saving mechanism. Measurement results show that the energy consumption of the group owner is always higher than that of the group member. Then, the proposed energy-saving mechanism is described in detail, which can reduce the transmission consumption of devices and balance the energy consumption of the group owner by switching the role of the devices. At last, the proposed mechanism is evaluated with simulation experiments, and results show that the proposed mechanism can reduce 11.86% energy consumption with a throughput loss of 2%.