In digital textile printing process, various factors affect printing quality on fabric. One of these factors is pre-treatment process. If this process is carried out to control chemical interactions between dyes and fabrics strictly, proper pretreatment solution must be prepared depending on fabric types. Otherwise, high printing quality never realizes. Thus, in our previous work, [1] we focused on pre-treatment process and investigated the impact on coloring characteristics such as optical density and ink penetration on fabric in changing thickener which was one of the key materials in pre-treatment solution to realize high printing quality. As a result, we demonstrated that using two thickeners having different chemical structures from each other was much effective to adjust above coloring characteristics on fabric depending on required printing quality. However, in this previous work, we couldn't investigate and discuss whether controlling other parameters of thickener enabled us to alter coloring characteristics on fabric flexibly. Thus, in this paper, we focused on molecular weight of thickener as a parameter to affect printing quality on fabric and investigated whether changing molecular weight was effective to fine-tune coloring characteristics on fabric or not.