The present study seeks to develop the board of director's principle and its effectiveness on the corporate governance instructions of Securities and Exchange Organization of Iran. After reviewing the theoretical literature on the composition and characteristics of the board of directors in the corporate governance principles of New York Stock Exchange, London Stock Exchange and Malaysia Stock Exchange and considering the social, economic, political and cultural conditions of Iran, dimensions and components of effective composition and characteristics of the board are determined. These are including Board Roles, Responsibility Separation, Chairman of the Board, Non-Executive Board Members, Board Composition, Board Commitment, Board Development and Improvement, Board Information and Communication, Board Evaluation, Re-Selection of Board Members and board compensation. Then, opinion of 30 experts are gathered and analyzed using the triangular fuzzy Delphi method, and finally the dimensions and components of the composition and the characteristics of an effective board are extracted. The results show that the principle of the Board and CEO included in the corporate governance instructions developed by Securities and Exchange Organization of Iran has some bugs including definition of major shareholder and characteristics of an independent board member. Also, Components such as definition of an independent senior member, disclosure of the number of meetings of the board of directors and committees, determining the training needs of board members, evaluating the performance of board members, etc. are not considered and require the consensus results of the present study.