The article is devoted to research of systematicity in criminal law and criminal legislation of Ukraine. Notwithstanding that this category is a basic concept for all cases of its application in the field of criminal law, yet the authors distinguish: 1) the system of criminal law as a branch of law; 2) the system of criminal legislation; 3) the system of criminal law phenomena determined by the criminal law and criminal legislation. In defining the system of criminal law as a branch of law new terms are suggested to be implemented, i. e. a «micro rule» and a «macro rule» of criminal law, their interrelationship and systemic significance being determined.