The present invention provides a system and a method for service continuity in heterogeneous wireless networks, which comprises a handover decision module and a session continuity module. The handover decision module is responsible for maintaining link layer association and network layer reachability in according to the underlying network conditions to fulfill the service requirement of applications. When acting as a sender, the session continuity module will select transmission path(s), reestablish the transport connection(s) and tag packets with session IDs and sequence numbers. When acting as a receiver, the session continuity module will identify and reorder packets using session IDs and sequence numbers, regardless of the IP addresses and ports of the packets. To sum up, the present invention can provide service continuity and multipath transmission for network devices.