Nowadays the business microblog register is an object of linguistic research because its structural and semantic properties require further investigation in terms of linguostylistics, discourse analysis and business rhetoric studies. The relevance of the work is due to the fact that today the register of microblogging and its semantic structure have not been studied in the context of business communication. The authors aim to find out what functions are performed in business messages of the social network Twitter. The work uses the methods of functional analysis and logic-semantic analysis. The study identified such properties of a business microblog, as hypertextuality, interactivity, dialogical and polycode nature, as well as spontaneity, business context, situational nature, expressiveness. Logic-semantic analysis revealed the following properties: the most frequent pragmatic-semantic relations (functional connections) between propositions are clarification, extension, causation and pragmatic commentary. Thus, the analysis of language material has shown that the business microblog genre is a result of mixing and contamination of oral and written business discourse registers, as well as a consequence of emergence of new technical means of communication. Functional and semantic analysis of propositions showed that the semantic structure is predetermined by the communicative intent of the addresser and, due to the small volume of messages, is built on the basis of two or three propositions connected by certain logical relations. Further studies on this subject can be conducted in the field of studying virtual language personality and general Internet linguistics.