It is necessary that forest roads be constructed according to standards considering the importance of forest roads in the forestry plans and sustainable management. The Standard Drainage system is one of the most important technical buildings in the forest road construction. Darabkola forests have been located in the central part of the northern margin of Alborz Mountains in watershed basin 74 which have been established in 1.5 km distance of sari. Darabkola forest’s area is 2612 ha. The effective factors on road drainage such as road width, cross and longitudinal slopes of road, slope of excavation and embankment ranges, longitudinal slope of ditch and basal area of ditch were measured in each 40 m of 1.5 km of forest road length. Then the sample point's locations were recoded using GPS (Global Position System) and the related map was prepared. The Culverts diameter and the Culverts distance of each other was measured in the current drainage system and the culverts location was also recorded using GPS. In addition, road route was tracked and recorded using GPS to obtain more accuracy. Finally, the drainage system of study forest road was compared with accepted standards. Results showed that there is significant difference between the current drainage system of Darabkola forest roads and accepted standards in some cases and the drainage system of these roads was evaluated in the medium situation. Key words: Culvert, drainage system, forest roads, global position system (GPS), Iran.