The article is devoted to defining the concept and essence of the principles of criminal executive law. The article analyzes the general theoretical concepts for defining the term “principles of law”. The author’s positions of the compilers of explanatory, etymological and other dictionaries on the definition of the principles of law are considered. The positions of domestic scholars in the field of criminal executive law on this issue are studied. It is noted that most definitions of the principles of criminal executive law are based solely on one aspect of criminal executive reality, which is the activity of execution of punishments. Based on this area of criminal executive activity, an idea of the current, basic provisions of the current criminal procedure law has been formed. The article emphasizes the mandatory consideration of such a direction as serving a sentence when determining the key, fundamental provisions of criminal executive law, taking into account the category of principles. This direction actually embodies the subjective composition, which according to the specifics of criminal-executive relations belongs to the sphere of serving sentences. First of all, this direction is related to the person of the convict, as well as other persons involved in this process. This category of persons also includes representatives of local authorities, self-government, public and religious organizations, etc. The article focuses on and expresses the author’s position on the definition of the principles of criminal executive law and mandatory consideration of key elements that fully reflect their essence. Such elements include the perception of principles as: 1) fundamental, conceptual ideas of the relevant branch of law; 2) criteria of subjective, human perception of events, phenomena within certain legal relations; 3) key elements of the structure and functioning of legal mechanisms. Given this, the principles of criminal executive law have the following meanings: a) doctrinal; b) perceptual; c) regulatory. The proposed elements fully reflect the substantive component of the principles of criminal executive law.