The music works of Baroque,especially Bach s keyboard poliphonic music,are important contents in the performing and teaching of free bass accordions nowadays.

In this dissertation, the construction and expression of free bass accordion are summerized from the angle of musical instrument subject, the main compositions to teach and play are.

The emergency of free bass accordion, which broadened the range of repertoires played on accordions, made it possible to accurately master polyphonic works created by composers like Bach.

Since the reform and opening up,the spread and inflow of international accordion information into China has displayed for China s accordion field the mainstay of international accordion,the free bass accordion,and it introduces the play of Bach s polyphony in Baroque Period into the firstclass music schools.