Owing to the formation of aggregation and gelation during storage, certain proteins and peptides exhibit limited applications in aqueous protein food products. The purpose of this study was to investigate the influence of homogenization and xanthan gum addition on the dispersion stability of Mytilus edulis hydrolysate (PHM). High-pressure homogenization (HPH) at 360 and 40 bar in the first and second values, respectively, and adding xanthan gum at a concentration of 1 mg/mL showed significantly improvement on the stability of the PHM solution. PHM-xanthan gum solutions (PHMX) showed the highest polypeptide precipitation rate and turbidity retention rate compared with those of PHM. Moreover, the centrifugal precipitation rate of PHMX without HPH was higher than that of homogeneous PHMX. After HPH treatment at 400 bar, the percentage of smaller particles in PHM and PHMX was increased, the aqueous system became more uniform, and the fluorescence intensity reached its maximum. HPH pretreatment improved the polypeptide dispersion stability and turbidity retention rate of PHM and PHMX and reduced the fluorescence intensity. The interactions of xanthan gum and polypeptide render the network microstructure more uniform under the conditions of homogenization, thus improving the dispersion stability of PHMX solutions. Therefore, under the premise of adding xanthan gum, HPH can better enhance the dispersion stability of the polypeptide in PHM.