Diameter, height and the trank shape indicators are generally important parameters in forestry measurements. The importance of these parameters is considered in cases such as the determination of tree volume and the wood reserve of stand forest and the relationship between the two parameters is also evaluated. Forest Mensuration through the application of statistical and mathematical procedures on the forest, developed very important mathematical formulae and equations in the growth and development of the forest, through which detrmination of a hard measuring parameter (indicator) can be achieved by an easy measured one. Our study emphasized on the relationship between height and diameter of Quercus trees in the Goulan heights. We developed an equation through which the height of trees can be calculated by their diameter. This is very important if we considered that measuring the hieght of trees requires suitable measuring equipments and experience, in addition to the long time required for measuring the height of trees inside (within) the forest.