Embodiments of the present invention provide a system and a method for transmitting data based on Peripheral Component Interconnect Express 9PCIe). The system includes: a PCIe switching network, multiple switch terminal devices, a managing unit, multiple host processing units, multiple terminal processing units, multiple hosts, and multiple terminal devices. After a PCIe data packet sent by a host is processed by a host processing unit, a new PCIe data packet that can be transmitted in a PCIe switch is constructed, and is transferred, by using a switch terminal device and a terminal processing unit, to a terminal device. The embodiments can break through a limitation about a single root node of PCIe and implement sharing of a PCIe switching network by multiple hosts.