A method for manufacturing a cylinder head system for a vehicle includes manufacturing a first main mold to integrally form an exhaust manifold for discharging exhaust gas from a cylinder and a first water jacket for cooling the exhaust manifold, manufacturing a second main mold to form a second water jacket for cooling a cylinder block, and connecting the first main mold to the second main mold. The mold includes a first main mold having a plurality of exhaust manifold molds and a first water jacket mold, each exhaust manifold mold being configured to form a respective exhaust manifold, and the first water jacket mold being configured to form a first water jacket for cooling the exhaust manifolds, a second main mold having a second water jacket mold, the second water jacket mold being configured to form a second water jacket for cooling a cylinder block, and the second main mold being configured to be assembled with the first main mold. The first water jacket mold may be disposed between the exhaust manifold molds.