This article is a study with the heading of moral philosophy in age of Enlightenment, to bring together Immanuel Kant, the great philosopher of Enlightenment age and launcher of a new age in history of philosophy and Ludwig van Beethoven, the great composer who was contemporary of him and launcher of a new age in music history. The first part of article is an investigation of the systems of metaphysical philosophy exposed by eminent philosophers since Platon to Kant in general. Henceforth, it is striven to reveal the metaphysics of Kant by means of his way of speculate about it in a different way than all philosophers before him and way of achieve philosophical revolution. The moral philosophy which is in central position of his system of metaphysics has been main theme of this article. In this study, research based on the exposition of moral way of life and world view by Kant and it's influence on the music of Beethoven. It is invesitgated in the last part of article as one of the very crucial example how the musical content of Ninth Symphony by Beethoven is determined by that influence. This work has been a milestone in the music history likewise the break a new ground in philosophy by Kant. Furthermore, year 2020 is coming across the 250th anniversary of birth of Beethoven was an inspiration for this article.