The harmony in this sonata is a mixture of the Classical music style and the Romantic music style. Romantic composers prefer simple harmonic structure, such as use of the primary triads. Harmony was mainly diatonic (major and minor harmonies), harmonic progressions were simple, and non-harmonic tones were not used as frequently as they were during the Baroque period. In sonata in A major, we can see Schubert used many I, IV, and V chords, and most of them are on the forte beat in each bar. It is an application of the classicism harmonic technique and classical style. But only useing the traditional classical harmony principle was not enough for Schubert to express his emotion. He further expands the vocabulary of harmony on the basis of maintaining the classical harmonic style. with his unique and novel harmony approach to strengthen the expression and meet the needs of different emotions, for instance, using chromatic harmony, dissonant chords and common-chord modulation.