The invention discloses a method, a device and a system for packet switching, and belongs to the field of packet switching. The method comprises the following steps: receiving an original switching request sent by an uplink switching module; copying the original switching request to obtain a plurality of switching requests, arbitrating the switching requests according to the states of ports connected to a vertical-horizontal cross switching module and a downlink switching module, outputting the obtained arbitration result to the uplink switching module; receiving cells sent by the uplink switching module; and according to the arbitration result, forwarding the cells to the downlink switching module. The device comprises an input request processing module, an arbitration module and an output permission processing module. The method, the device and the system have the advantages of realizing the intercommunication between the packets, expanding the number of ports of the packet switching system, enhancing the switching capacity, simultaneously being compatible with the original SM system, and reducing the cost of the switching system, along with strong expandability.