The purpose of this study was to investigate the effect of the structure of reactive dye on cotton ink-jet printing. Cotton fabric was printed upon with three commercial cellulosic reactive dyes which are based on the similar chromophore and possess different numbers of reactive and anionic groups. Colour yield and absorbed dye fixation of the printed cotton were evaluated at various pHs. The ink-jet printing was carried out on a HP DeskJet 5150 printer at 1200dpi, and then the printed cotton fabrics were air dried and then put into a steamer to fix the reactive dye on to the cotton fabric. The results indicated that the absorbed dye fixation levels increased by decreasing the numbers of anionic groups and appeared to be dependent of reactive group’s numbers. All reactive dye based inks are demonstrating excellent to washing and dry/wet crocking colour fastness. The light fastness of each reactive dye based ink fixed to cotton fabrics was mordant.