After experiencing the long development and evolution of ancient and medieval times, the common law reached the peak of formation stage in the 13th century, then gradually declined, becoming chaotic, lacking certainty and authority in 16th and 17th century. At this time, the Roman citizen law and its homologous cannon law expanded rapidly on the European continent, along with the idea of establishing a strong, centralized authoritarian government against the common law heritage of England and its nationality, making the common law encounter an unprecedented crisis. The United Kingdom faced a difficult choice between completely following the Roman law and insisting on inheriting the common law back then. With regards to this topic and the issues raised by it, jurists have expressed their views and debated endlessly on the proper and authoritative nature of the common law. Through the discussion of Edward Coke, John Selden and Matthew Hale's views on the authority and legitimacy of common law back then, I will present the main views of English jurisprudence on the legitimacy and authority of common law in the late 16th and 17th centuries.