In the first half of the nineteenth century, London provided an excellent environment with abundant musical activities that attracted outstanding musicians all over the Continent to be here for their careers. Both the Industry Revolution and the French Revolution brought essential changes of political and economical activities into London, and consequently influenced the musical environment. In addition, the enthusiasm for music, from the Royal to the civics, provided a stage for the development of piano music. This thesis discusses the musical environment and social condition of London in the first half of the nineteenth century, their influence to the writing and performing of piano sonatas by ¡§the London Pianoforte School.¡¨ There are three main chapters in this thesis. Chapter One discusses the influence of social transition to musical activities and points out the social phenomenon of music, the performing environment, the demand of piano production, and the technical improvement of piano making. Chapter Two investigates the writing of piano sonatas by ¡§The London Pianoforte School¡¨, including the forming of the school, musician activities in London, and situations about of the piano sonatas that were written and published. Chapter Three examines the functions of piano sonatas of ¡§the London Pianoforte School¡¨, and compares the differences between sonatas written for teaching and for public concerts purposes, focusing on writing techniques for different functions.