An engine system includes: an intake line through which fresh air flows; an exhaust line through which exhaust gas flows; an exhaust gas recirculation (EGR) system which recirculates some of exhaust gas to a combustion chamber; a turbocharger having: a turbine that rotates by the exhaust gas; and a compressor rotating by the rotation of the turbine; an intercooler disposed in the intake line at a rear end of the compressor; an intake bypass line penetrating the intercooler from the intake line, adjusting the amount of intake gas to be supplied into the combustion chamber, and merging into the intake line at a front end of the compressor; a recirculation valve disposed in the intake bypass line; and a controller controlling opening and closing of the recirculation valve so that some of the intake gas is supplied into the intake line through the intake bypass line.