This thesis is focused on two Violoncello compositions of J.S. Bach ：Suite No.5 in C Minor, BWV 1011 and Sonata in G Major, BWV1027. Introduce the composer's life, compositional stages and the background that the work is created. Furthermore, do the analysis of the work and annotate it. In the end of the thesis, propose the research about performing of interpreting.

This thesis contains six chapters. And there are three focal points. The first one is a discussion of the historical background. The second one is the analysis of the suite and the sonata about compositions of J.S. Bach. The last one is performing and interpreting.

Ⅰ. The discussion of the historical background：

We introduce the Bach's life, compositional stages and the background that the work is created. Include a created source of J.S. Bach two compositions, music score, and the background of bass instrument and bow.

Ⅱ. The analysis of the suite and the sonata：

Departing from the inspirations and background of suite and sonata, then discuss each movement in details. The speed, tonality and motives of the suite and the sonata are included in the analysis.

Ⅲ. Performing and interpreting：

We probe into the right-hand and the left-hand technique and compare the dependences and differences of the techniques in every movement. Include the bow rule, dynamic, articulation, chord, interval, vibrato, ornamentation, and shifting position etc.