This paper presents the design of alert message and message segmentation method for the Terrestrial DMB Automatic Emergency Alert Service Standard. This paper begins with the introduction of the standard and some background. The alert message contains the essential information of the alert. Structured information is represented as coded fields and the unstructured as short sentences. Design factors of each field are analyzed first. Next each field’s semantics and syntax are described. The message segmentation method is presented next. The previous study selected FIDC as the message delivery channel. However, in most cases, the size of the alert message exceeds the maximum size of FIG, which is the basic unit packet for the channel. The current T-DMB standard does not support the segmentation method for FIDC. To solve the problem, this paper proposes an elegant segmentation method that garantees reliable, flexible, and fast receiver characteristic. This paper concludes with some additional tasks that should be resolved before the full-time alert service.