Object tracking is an important application in Wireless Sensor Network (WSN). High-accuracy and energy-efficiency are key requirements. In this paper, we propose a novel face-based object tracking protocol (FOTP), which is used to track the object with low energy consumption and high quality. FOTP combines a hexagon algorithm with face-architecture system model, which can provide precise detection and efficient tracking. Firstly, soldier nodes observe the object and elect a near node (NN) which is the nearest node to the object. And then, the NN tracks the tracked object (TO) and predicts its next position by hexagon algorithm. Furthermore, candidate faces will be woken up by the NN and responsible for continuously tracking the coming TO. Being compared with previous works, FOTP tracks object with limited sensor participants. Simulations show our protocol can not only support efficient tracking but also conserver more energy.