As the importance of military usage of Unmanned Aerial Vehicle (UAV) increases, developing cost-effective UAV system is also being emphasized. In this paper, we integrated Predictive Ground Collision Avoidance System (PGCAS) used in military jet fighters into UAV to develop a low-cost flying safety system that can help an operator to concentrate fully on their missions setting aside the danger of ground collision. By adjusting the original PGCAS algorithm appropriate for fixed-wing UAV applications and constructing processor in the loop simulator using small flight control computer and X-Plane 10, we were able to show that the modified algorithm can give terrain-neighboring as well as safe ensured flight path.