A method for trigger information transmission and protocol conversion is provides, and the method includes: an MTC-IWF which has received trigger information about an MTC device acquires routing information of the MTC device through a subscribed serving network element, the MTC-IWF transmits received trigger information about the MTC device to a serving core network node of the MTC device through an SMS core network node; the serving core network node of the MTC device transmits the trigger information to the MTC device; in the above process, the MTC-IWF or a dedicated IWF or an SMS router implements signaling conversion between an MAP protocol and a Diameter protocol. A system for trigger information transmission and protocol conversion is also provided for implementing above method. It is possible using the method and system to transmit trigger information through a T4 interface and establish a process of converting between an MAP protocol and a Diameter protocol.