A discourse means its communicative purpose and the corresponding consequence. The construction of a whole discourse is through interaction between producer and receiver. The pragmatic function of external publicity is of specific ideology feature, and the publicity of value and ideology is realized through the audience's active response. Under the trend of globalization, external publicity is not confined to static verbal discourse. So the discourse construction of external publicity is in multimedia and interactive environment, and is of positive discourse trend. Combined with the register theory, through analyzing the successful publicity cases, this paper suggests several discourse construction model of the multimedia interactive external publicity.