The chitosan nanoparticles can be prepared by ionotropic gelation method in dispersion system. Chitosan nanoparticle has advantages of both the chitosan and the nano particles, and so it has a wide application in the textile finishing field. In this paper, the effects of the concentration of TPP, Span-80, deposited time and pH value on the diameter distribution of the chitosan nanoparticles are discussed in order to obtain the optimized preparation technics of steady state chitosan nanoparticle. The results show that chitosan nanoparticles are successfully prepared by ionotropic gelation method. Under the optimized preparation technics, chitosan nanoparticles disperse homogeneously in the system and have a good steady state. The average diameter of chitosan nanoparticle in the dispersion system is 20.82nm. Compared with the ordinary silk fabric, the B. mori silk fabric treated with chitosan nanoparticle dispersion system has better deepen effect of reactive dyes. The chitosan nanopartilce dispersion system is helpful to improve the dye uptake and dye fixation of silk fabrics.