The metal strings took the place of silk strings to the instrument ”Er Hu” in 1950's. Since then, silk- string Er Hu was almost eliminated. Under the requirement of the ”Modern Chinese Traditional Music”, metal-string Er Hu has its own advantageous position. It's also brought Er-Hu into a new field. However, is silk-string Er-Hu really valueless? The catgut in violin, which was almost forgotten by the Western world, was polished up again nowadays. Moreover, its musical development has been becoming multiple. The voice of silk- string Er Hu is tender, natural and powerful. It has an endless echo. The sound of silk- string Er Hu is soft and touching. A vibrato of it will mix people's soul and body together. Music is not performance only. More people expect to enjoy themselves. So, the research focuses on the interview and questionnaire between the performers and the audience. It also shows the unlimited development of silk- string Er Hu. Meanwhile, it exposes some questions on the instrument and the performance.