A range of novel cationic starlike polymers (poly(Pen-g-MeDMA) were synthesized through atom transfer radical polymerization (ATRP) by core-first method. The tetrafunctional initiator (Pen-Br) was prepared by esterification of pentaerythritol with 2-bromoisobutyryl bromide. [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (MeDMA) was polymerized in H2O/EtOH medium using Pen-Br, Cu(I)Br, 2,2-dipyridine as an initiator, catalyst, and ligand respectively. The results indicated that the cationic charge density of the poly(Pen-g-MeDMA) were high and pH-insensitive. The poly(Pen-g-MeDMA) could be used as a cationic fixing agent to remove dissolved and colloidal substances from pulp, markedly improving the efficiency of retention aids.