Embodiments of the present invention relate to the field of communications, and provide a data transmission method, apparatus and system. The method includes: detecting whether data transmitted in a received GTP-U data packet is data of a predetermined type; if a result of the detection is that data transmitted in the GTP-U data packet is data of a predetermined type, decapsulating the GTP-U data packet, to obtain the data of the predetermined type and a destination address of the data of the predetermined type; and sending the data of the predetermined type and the destination address to a message gateway, so that the message gateway forwards the data of the predetermined type according to the destination address. A gateway includes: a detection module, a decapsulation module, and a sending module. A message gateway includes: a receiving module and a forwarding module.