The first step in designing the cooling system of a turbo generator is the ventilation system analysis. The present paper deals with a comprehensive investigation of flow parameters of a high power turbo generator. By employing the lumped-parameter model in the closed circuit of the flow network, the cooling medium flowrate and pressure drop in each element is calculated. In addition, considering the fan characteristic curve, the operation point of the fan is specified and consequently the fan can be further optimized. Furthermore, the results are verified by the equality of the total pressure drop experienced by flow and the total pressure rise generated by fan and rotor speed. The results are in good agreement with the available official data.