Abstract. The subject of nationality includes to study a set of regulations based on which an individual nationalitystatus to a certain government can be determined. The regulations are ordained by eachcountry separately to determine its citizens. As a consequence, if someone is not considered as a citizen in territory of country and based on the regulations, he/she is considered as a stranger whether the nationality of another country can be related to him or not. Therefore, the major consequence of these regulations in the country is to isolate the citizens from the strangers. In the present study, a brief description of the nationalityprinciples and description of various types of nationality are given in addition to investigating the legal systems governing thenationalitywhich are divided into two main sections including the blood system and soil system. Also, the reasons of advocacy of these two nationality systems have been discussed and compared separately.