Ionic liquid 1-butyl-3-methylimidazolium chloride BmimCl as an assistant agent was applied in degumming and dyeing of silk. The effects of ionic liquid on the degumming rate，degree of whiteness and dyeing performances of silk were investigated. The obtained results indicated that degree of whiteness of silk was obviously enhanced under acidic condition with ionic liquid as assistant agent. The degumming rate was about 21% and degree of whiteness was more than 80 when the volume concentration of ionic liquid was 5%，pH value was 2 and bath ratio was 1∶50 at 98℃ for 1 h. After degumming with ionic liquid the silk was dyed and the dyeing performances were determined. The colour depth（K/S value）was enhanced to 21，dye-uptake was 84%，dry crockfastness was 5，wet crockfastness was 4 and soaping fastness was 5. The obtained dyeing performances of degumming silk with ionic liquid were supper than that of the conventional degumming silk.