The Ytype and straighttype bypass structures for twostage turbocharger were established and their flow resistances were compared by CFD software. The results show that the flow loss of the Ytype structure is larger than that of the straighttype structure when the bypass valve closes fully, but is smaller when the valve opens. For the same bypass structure, smaller opening will lead to greater loss. The flow loss will became relatively larger with the increase of valve opening due to the increase of air mass through bypass valve.