Ink drop spreading is an important factor influencing the ink dots distribution which determines the color performance of reactive dye inkjet printed cotton fabrics. In order to control the ink drop spreading, a higher fatty acid derivative (PT) was introduced in the traditional pretreatment solution of sodium alginate. When compared with the untreated fabric, the ink drop spreading area was reduced from 104.9 to 92.5 and 72.3 mm2 on sodium alginate treated and sodium alginate plus PT treated fabrics, respectively. The ink dots on the inkjet printed fabrics with the pretreatment of sodium alginate plus PT were narrow and short. Colorimetric values indicate that the color performance of sodium alginate plus PT treated fabrics was better than that of sodium alginate treated fabrics. Thus, the color performance of reactive dye inkjet printing was improved by the ink droplet spreading inhibitor PT.