The International Association of Classification Societies(IACS) can trace its original back to the International Conference on Load Lines of 1930 and was established in 1968. Long before the formal foundation of IACS, a number of working parties existed to carry out studies of specific topics concerning technical rules of classification. The general terms of reference of the working groups of IACS are to draft unified rules and regulations between Societies, to study safety standards at the request of the International Maritime Organization(IMO) and to prepare unified interpretations of technical regulations of international conventions. As an associate member since 1975, the Korean Resister of Shipping has been actively attending the meeting of IACS working parties. In this paper, summaries of major agenda of the working parties including history of unified requirements and relevant technical tendencies are explained for the purpose of providing better understanding of the rule development.