Abstract: According to stipulations what is stipulated in Article 9 of Rome Ⅰ Regulation， it has already been an objective fact that sovereign states recognize the priority validity of overriding mandatory provisions under certain circumstances. The academic circles have， however， been arguing about relevant problems concerning overriding mandatory provisions all the time. The main reason for of the long-term existence of such dispute is that the scholars are too committed to the applicable methods of such kind of rules rather than instead of focusing on the nature of overriding mandatory provisions being private law rules. In theory effect， overriding mandatory provisions are obviously private law's in nature， which has not only determined that the discussion of relevant problems should be held within the scope of Private International Law，but also determined that they have natural legal effect at home. At present， there is still no legislation on how to apply foreign overriding mandatory provisions in China.， When filling relevant legislation， and legislators should pay special much attention to legal issues about discretion， the consequences of applying the mandatory rules of a third state and the principle of the autonomy of will.

Key words: private international law, overriding mandatory provisions, legal effect, Rome Ⅰ Regulation