One of the problems of tunnels is lacking enough fresh air for passengers inside the subway. Also, as a result of the friction of the train with the railways inside the tunnel, high heat is generated. So, the design and calculation of an efficient ventilation system are critical for the tunnels. There are several methods used to determine the most effective tunnel ventilation systems while reducing fan energy costs, including their operating performance. The main task of an optimal tunnel ventilation system is to determine the quantity, location, and function of fans to distribute the required fresh air flow at the lowest possible cost. The main parameters for selecting a suitable fan that meet the optimal design of the tunnel ventilation system are the ventilation rate (Q) and the static head pressure (H). Both Q and H of Cairo Metro Line 3 were studied and calculated under different conditions of ventilation design from the obtained data. The amount of the ventilation rate by the fan was taken 80 m3/s which is the actual air flow rate taken from data of the National authority of Cairo Metro No.3. In addition, a comparison is made between various methods to determine the most effective tunnel ventilation system. The static head pressure( H )was calculated. According to the American Brattice Cloth (ABC) rigid duct method, the static head equals to 1171.5Pa , which is the most economical value that is giving the lower power consumption and rate of ventilation.