The main purpose of this work is to optimize the earthmoving machinery utilization in the forest road construction, by minimize the operating cost. That goal may achieve by the optimal distribution of the machine combination in the construction sites, with the ability of renting additional machines. Economical mathematical model has been developed for calculating the effective structure of the machine group to achieve the required productivity. The possibility of hire and rent machines allows the manager to improve the technical economic decision for the machines operation. By using the developed model it can gives good results to having better decisions for planning and designing the earth working operations in the road construction companies, renovation of the machine parks, as well as the choosing the best option for using the existing machine combination, predicting the duration and predicting the cost of the whole work.