Importance of detecting obstacles around construction machines increase rapidly. The millimeter-wave radar is the most useful sensor to keep to detect obstacles in the current technologies. because of its good performance under severe conditions. The signal processing algorithm of this radar is developed, for the using in working conditions by means of eliminating signal fluctuations and instabilities caused by its environments. The developed millimeter-wave radar has a reasonable performance, for example, detecting the rear side of automobiles and many types of construction machinery from the distance of 100m.