As a new approach to surface modification, polyelectrolyte brushes have been widely studied. Some researches on exploring core materials and brush layer materials have been carried out while the application field has been expanded, with some breakthroughs acquired. The latest research results in this field was summarized, and cationic spherical polyelectrolyte brushes were selected as the new retention and drainage agent in papermaking industry to improve the utilization ratio of raw material and paper properties. In order to fully apply weak-polyelectrolyte brushes in more fields, the influence of external factors on its mechanism should be deeply studied.