A block type pigment dispersion fixing agent for inkjet printing contains components as follows: A, a polymer block with an anchored group, B, a hydrophobic cross-linkable polymer block and C, a hydrophilic polymer block with a crosslinking point. A preparation method of the block type pigment dispersion fixing agent comprises the following steps: synthesis of the polymer block with the anchored group, synthesis of the hydrophobic cross-linkable polymer block and synthesis of the mPEGMA-r-GMA. According to the pigment dispersion fixing agent, pigment particles can be crosslinked and fixed, and the stability of ink is maximized; the dispersion fixing agent and cotton base fabric can be subjected to a chemical reaction, so that pigment particles are bonded to the surface of the fabric, and the fabric is not prone to decoloration in a friction washing process; additional hydrophobic film forming resin need not be added, and the fabric keeps original softness as much as possible after printed.