Johann Sebastian Bach (1685-1750) and Frederic Francois Chopin (1810-1849) respectively resemble the outstanding musicians of Baroque and Romantic periods. Bach’s “Well-Tempered Clavier" is one of the typical masterpiece that symbolize Baroque polyphonic music during the period. It features precise structure, rational logic and concise theme, which contribute to its lofty status among the history. Chopin etudes is his most representative and significant works which transform the mechanical and plain training mode of traditional etudes to not only technique but also features rich musicality, which greatly enhances the expressive power of the Etudes. This thesis is in exploring the musical link between the music of Bach and Chopin and focusing on analyzing the compositions of each composer to expound the characteristics of Bach and Chopin. Thus, the thesis explained the analysis through analyzing the harmony in both Bach’s “Well-Tempered Clavier” Book 1 No. 1 and Chopin Etudes Op.10. No. 1 By using comparison of both repertoires, the thesis then indicates the relationship and similarities between Bach and Chopin’s compositional writing in terms of expansion of tonality.