In this paper, we focus on the flight safety of human-operated UAVs in restricted airspace and design a human-in-loop assisted piloting scheme, which contains a new assisted piloting algorithm and the corresponding hardware and software. In the design process of the assisted piloting algorithm, the degree of intervention of the assisted piloting on the manual operation instructions is considered to be reduced under the premise of ensuring safety, and the scheme does not interrupt the mission process of the UAV and does not generate additional safety risks compared with traditional schemes such as forced landing. The compatibility with various flight controllers has been considered in the hardware design process to make the assisted pilot circuit more versatile. Finally, based on the Gazebo simulation platform, semi-physical simulation experiments are designed to verify the effectiveness.