UAV (Unmanned Aerial Vehicle) swarms are being utilized to launch military attacks due to its technological development. At present, there is a lack of countermeasures against such attacks. In this article, we propose to use GPS spoofing to deceive the UAV swarm's location sensing system as a countermeasure. Based on two open-source tools, ROS and Gazebo, we build a simulation platform of the UAV swarm position perception, and design experiments to deceive the UAV swarm's location sensing system. Experimental results show that two UAVs in flight can be maneuvered to collide through GPS spoofing, which can be a potential defense approach against attacks using UAV swarms.