"The Nasseri Law" is a treatise on the necessity and necessity of compiling and writing the law during the Nasseri period written by Mirza Saeed Khan Ansari, Minister of Foreign Affairs. Mirza Saeed Khan was the Minister of Foreign Affairs of Iran for 25 years, and this continuity in the ministry motivated him to carry out reforms in the country's situation. The reforms and measures that had to be taken for the development of the country had to go through the path of law, and this was not possible until a comprehensive and solid law was compiled and had no enforceable ability. Just as most intellectuals of this period also emphasized the necessity of compiling the law and had written treatises on this subject. In this research, the treatise "The Nasseri Law" has been examined using a descriptive-analytical method and content analysis, and it seeks to respond to the purpose of writing the book "The Nasseri Law" and the author's understanding and representation of the concept of "law". Considering Mirza Saeed Khan's position as Minister of Foreign Affairs and the relationship with Western countries and the challenges facing Iran in its relations with these countries, the necessity and existence of law is emphasized by him