Abstract: Disclosed is a new air intake system of an engine including a blow-by gas flow line configured to allow blow-by gas to flow into an intake manifold by recirculating the blow-by gas using a pressure difference according to load of the engine, an intake gas supply line configured to allow intake gas to flow therethrough, the intake gas supply line including a throttle valve configured to control an amount of the intake gas and a turbocharger configured to compress the intake gas, a new air supply line branched from the intake gas supply line and connected to the crankcase, the new air supply line allowing new air to selectively flow into the crankcase, and a new air bypass line configured to allow, when a part of the intake gas is selectively bypassed by the pressure difference, the part of the intake gas to flow into the crankcase.