The dye fixation process by the contact-type dry heat fixation (CDHF) technique was investigated when cotton fabrics are dyed with a reactive dye by the ink-jet printing. The dye fixation ratio was measured as a function of the water regain of fabrics and the temperature at the fixation treatment. At first, the time dependence of the water regain and the dye fixation ratio during the treatment was observed. Although the water regain drops sharply within 2 seconds, the practical level of dyeing was achieved if the fabrics are treated with enough amount of water and with high enough temperature. The amount of water and the temperature required are 29 wt% and 120 degrees C, respectively. The diffusion of dye molecules into the inside of the polymer matrix was confirmed by the model experiment using a cellophane film. In this dyeing system, the diffusion of dye molecules occurs very quickly, followed by the relatively slow dye fixation. Water molecules are very good plasticizer for the cotton fiber. The activation diffusion model may successfully describe the diffusion behavior observed in this study rather than the pore diffusion model which is often used for the explanation for the dip dyeing of cotton.