Topicality of the problem under investigation is conditioned by implementation of competency oriented federal state educational standards and professional standards into the practice of blue-collar workers training, the mentioned standards being intended to disclose the host of functions of various blue-collar occupations and WorldSkills standards reflecting modern world trends in the field of formation and development of blue-collar workers' professional competences. In the meaningful aspect, today's standards identifying requirements to blue-collar workers training will define principles of selection and formation of competency oriented subject matter of training; however, the choice of training technologies quite often remains beyond the training standards. At the same time, the competency oriented training of blue-collar workers shall envisage application of the activity approach to organization and realization of the training and, consequently, of technologies of training based on the activity approach. The modular technology of training based on points of European concept of "Modular employable skills" can be one of such technologies. The purpose of the article is description of the authors' modular technology of forming of workers' professional competency under conditions of corporate training. The modular technology is described herein as exemplified by formation of professional competency of workers of the machine-building industry in field of lathe part machining. The article also includes results of an experimental approbation of a developed modular technology in conditions of plants' training centers. The investigation's leading method shall be a pedagogical educational experiment in process whereof the modular technology of forming of workers' professional competency which has been developed by the authors shall be approbated, the mentioned workers belonging to the machine-building industry in field of lathe part machining, whereas a worker's professional competency is regarded as an integrated aggregate of core competencies and occupational personal properties which lie in the base of the selection and structuring of the subject matter of training. Materials and methods: the pedagogical educational experiment allows exposing the efficiency of complex formation of the professional competency in trainees by means of applying of the modular technique of training and methodological support, that is, educational elements developed in line with requirements of Modular employable skills concept and supplemented with a set of production tasks performed directly on the job under the tutor's guidance. The following methods were used in process of the research: theoretical (analysis, synthesis, deduction and induction); diagnostic (methods of analysis and systemizing of scientific pedagogical literature; generalization and classification); empirical (modelling). The key results described in the article: the professional competency model of the machine-building industry workers; the modular technology of formin...