Ventilation network theory and its application in the ventilation of highway tunnels are discussed in the paper. The calculation formula for the ventilation pressure of the traffic air in the ventilation network theory is deducted. The treatment methods for the ventilation fan air, natural air and airs with other pressure sources in the ventilation network are presented. Calculation analysis is made on the ventilation scheme of Xuefengshan tunnel by means of the calculating program of the highway tunnel ventilation network and good engineering results have been achieved.