­^¤å´£­n¡R Variation technique has always been one of the way of composing used by composers both in eastern and western music. During Beethoven's creative time, he worked on variation both technique and musical form frequently. Before 1800, he composed pieces based on variation technique for keyboard including 12 piano variations, few chambers and piano duets. After 1800, he started using variation more intensively. The pieces he wrote include in chambers, concertos and symphonies. Until 1815, the technique of variations became character on the late period of Beethoven. In this thesis, The definition of variation will be introduced first. The historical background of variation will be discussed from Middle age to Classic period. Before 1823, the types of variation can be differentiated as the independent variations and variation movements in large works. And the technique could be divided into four types which are ostinato variations¡Bcantus-firmus variations¡Bfixed-harmony variations and melodic variations with fixed harmony. And the form of variation can be divided into three types which are strophic variations¡Bhybrid variations and genre variations. Then, three string Quartets from different periods¡Bsymphony No.3 and some piano variations will be discussed from the point of view of Beethoven's variation technique. And 5 pieces from piano sonatas of Beethoven's works-- Op.14 No.2 II movement, Op.26 I movement, Op.57 II movement, Op.109 III movement, and Op.111 II movement-- will be described in detail on the background of composing and form analyzing. Finally, conclusion will be given. By adding variation movements to classic sonatas, Beethoven experienced the new technique of variation, and made these 5 sonatas much more unique and with variety.