A data processing method is provided for forwarding data in the case of handover between heterogeneous networks. The data processing method includes: when a user equipment (UE) is handed over from an originating network to a target network, receiving, by the originating network, a data forwarding address obtained by the target network; creating a data forwarding tunnel between an originating network gateway and a target network gateway according to the data forwarding address; and forwarding data to the target network through the data forwarding tunnel. A data processing device is also provided. The lossless data processing solution can overcome the problem of data loss in the case of handover between heterogeneous networks in the existing technology, reduces the time of user service interruption and enhances the user experience.