This study was aimed to explain the essence of Hydroxylammonium hydrochloride(H.A.) effect on degummed silk fiber increasing the colour sites due to oxime generating reaction. H.A. in aqueous solution caues to increase the amount of [H+] and reduce pH values as the concentration of H.A. increases. The rate of [H+] absorption of silk fiker in acidic solution differs on the basic of solution pH and shows a specific uptake in each pH, the lower the pH of solution, the higher the amount [H+] absorption. The pH of solution after treating of silk fiber in H.A. and HCl, showed more remaining [H+] in H.A. solution due to [H+] releasing under the procedure of oxime production. Also it was revealed that in higher concentration of H.A. the reaction for oxime fixation in silk fiber carried out stonger and as a result the bigger gap with acid uptake curve appeared. FT-IR analysis of silk fiber treated with H.A. revealed the creating of intermolecular H-bond at the 2,981-2.930 cm-1, which was not appeared for nontraeted silk fibers and shows H-bond between N-OH group in oue chain and C=) group in another chain of silk protein. Colourimetry of dyed silk fiber after H.A. tratment showed that the silk fiber treated with the high concentration of H.A. compare to low concentration, absorbed more dyeing molecules and so Showed less percontage of Whiteness.