A main purpose of mine ventilation is to control the airflow in a ventilation network properly. The ventilation network analysis is used for this purpose. In this analysis, the airflow distribution is calculated using the data about the mine structure, the airflow resistances, and the temperature etc. However, it is often necessary to know the airflow resistances that achieves the required airflow rates in the actual ventilation practices. This means that the airflow rates are data and the resistances are the result of the analysis. There is almost no method to solve the problem directly. Therefore, the airflow resistances are often estimated by trial and error method using the conventional ventilation network analysis. It is not so difficult if the number of the target roadway is only one. The difficulty increases if the target roadways are more than two as they mutually interfere. The authors find the method to estimate the airflow resistances without essential change of an usual ventilation network analysis program by using the fixed flow roadways. The method can be applied even when the target roadway is not able to be changed its resistance. By applying this method, the airflow resistances that minimizes the power for ventilation and satisfies the required airflow distribution are estimated at the same time. These results will be described in the paper.