Abstract: Forest road is one of the most important ways to access the forest and its own activities. It should have some standard qualities and also had the list harm for nature. One of the most important qualities of forest road is limited of two sides to developing of natural forest. Alder tree is the first kind of trees that grows in northern forest of Iran closed to the constructed roads. This research was done in Mazandaran forest (Darab Kola district) to evaluate how Alder grows in the two side margins of roads. Twenty half plot (upper and lower road margins) with a size of 1000 m2 in one kilometer length of this road was selected and twenty face to face Alder trees closed to the road were sampled to take two cores in a face and back of road at the DBH level. After analyzing the data with a simple variance and comparing annual rings (curves), diameter, height and growth by simple and joint t-test, the results show that there is no significant difference between growing in upwards and downwards of road and also between diameter and height of tree in two sides of road. Most diameter distribution classes of trees were in a 15-20 cm. To consider more about this matter, study of different width and slopes of forest roads in a various forest stands was proposed.