Since constitutum possessorium lacks the external representation of the alternation of real rights, the third party cannot know and judge the alternation of real rights. In order to protect the interests of a bona fide third party and the transaction security, it is necessary to impose clear restrictions on the legal effect of constitutum possessorium. Through researching and analyzing the legislations regarding the legal effect of constitutum possessorium in different continental law countries, we draw a conclusion that since the possessor has no rights to claim against a bona fide third party, there comes a fundamental difference in legal effect between constitutum possessorium and other modes of the conceptual delivery. On the basis of above analysis as well as the relevant provisions in Chapter Two, Section Two of China’s “Property Law” and Article 18 of Interpretation of the Supreme People’s Court on Several Issues concerning the Application of the Property Law of the People’s Republic of China (I), we have proposed several suggestions on the improvement of constitutum possessorium in the Civil Code.