The analysis of LOS(Line-Of-Sight) is defined as an "unobstructed view between two points". The LOS results may be influenced by terrain source, algorithm/interpolation method, etc. In the area denies any access and flight over, LOS results would be doubtful because of low precision of terrain data therefore have limitations of referring to many military applications. Using LIDAR data, LOS Analysis was performed by changing DTED resolution(1$sim$30m) and LOS distance(50$sim$2000m). The results of experiment shows that LOS analysis for small area, such as DMZ surveillance, were heavily influenced by DTED resolution.