Machine type communication system, data transmission method and device thereof

Disclosed are a Machine Type Communication (MTC) system, and data transmission method and device thereof. The invention relates to wireless communication field and can be used to reduce signaling interaction among different Public Land Mobile Networks (PLMN) to save signaling resources. An original MTC interworking function (MTC-IWF) in home PLMN (HPLMN) implements data transmission with a core network control device in VPLMN through an agent MTC-IWF in Visited PLMN (VPLMN). Thus the original MTC-IWF in HPLMN does not need to establish and maintain connections with each core network control device, so as to reduce signaling interaction among different PLMNs and save signaling resources.