To legally mandate a minimal ratio of female members of board of directors may bring about apparent benefits to listed companies as well as their current and potential employees. But most listed companies have a controlling shareholder which may compromise the effort to promote gender diversity in board. The relative shortage in the supply of qualified female candidates may also hinder the actual implementation of such a legal mandate.  A few institutional designs informed by law and economics and practice in overseas market are therefore suggested in the talk to pave the way for issuing and implementation of such a legal mandate.