The authors pursue the aim to study the formation, evolution and regularities of the Common Foreign and Security Policy of the European Union, as well as the European Union diplomatic service.  The methodological basis of this study consists of historicism, systematism, analysis, statistics and comparative jurisprudence. The author's position is based on the legislation and ideas of representatives of the competent scientific community on the issue of common foreign and security policy of the European Union, the regularities of its improvement and development. On the basis of the legal analysis of the European Union law the differentiation of the characteristic features of its foreign policy is carried out as well as issues of legal regulation of the diplomatic service are raised. As a result of the study the significance of the right choice of organizational and legal forms of development of any sphere of the integration process and, in particular, common foreign and security policy, not only for its effective functioning, but also for further progressive development of the integration process as a whole has been revealed.