Abstract: To improve the sericin protein stability，the paper discuss the the performance change after the fixation of sericin by GA.Based on the test of moisture regain, white degree, silk protein stability, mechanical properties and the coefficient of thermal conductivity, the infrared spectrum of the cocoon silk ,analysis and discuss the performance change after the fixation of sericin.The experimental results show that, sericin fixing treatment effectively reduced the water soluble and improve the silk protein stability; The moisture regain decline rang from 1% to 4%;The breaking strength and elongation at break are increased, while the initial modulus declined, that is to say the softness increased after the sericin fixing. The coefficient of thermal conductivity of the cocoon silk changes very little after the sericin fixing, only a difference of about 2%.there are some different peak shape, peak position and different peak height after sericin fixing of the characteristics of the peak in Infrared spectrum. The wave number of some characteristic peak move location, that is to say the molecular structure of cocoon silk has a certain degree of change.

Key words: sericin fixation by GA, sericin, stability, coefficient of thermal conductivity