This research investigates the swarm unmanned aerial vehicle (UAV) formation and obstacle avoidance problem. A linearized fixed-wing aircraft model is adopted equipped with autopilot. It involves a task for five UAVs to patrol along a square area, forming a loose formation where strict relative positioning is not required. Inspired by bird flocking behavior, a formation method is employed incorporating attraction, repulsion, alignment, regulation and side force. When a UAV approaches an obstacle, from the UAV's perspective, the obstacle moves towards it, resembling a hunting scenario where the hunter gradually closes in on its prey. Naturally, an anti-predation strategy is introduced to achieve obstacle avoidance for the UAVs. Relevant parameters are optimized and simulation results demonstrate the feasibility and effectiveness of the proposed approach in this work.