Abstract: Proper dyeing parameters and mordant dyeing process are required to improve the superficial color depth on silk fabrics and color fastness of the natural dye mulberry sorosis, and maximize its color performance, A study is therefore performed on this paper to discuss the stability of the natural dye mulberry sorosis and its mordant dyeing effect on silk fabrics through the testing on the absorption spectra of mulberry sorosis dye solutions, the superficial depth(K/S、ΔE*) and the dyeing fastness of the dyed silk fabrics. The experiments show that natural dye mulberry sorosis has satisfactory color feature under pH 4 and 80℃. The mordant dyeing, especially the post-mordanting dyeing can greatly improve the performance on both the dyeing depth and the color fastness of silk fabrics dyed of the natural dye mulberry sorosis.