AbstractCellulose etherification with 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHPTAC) was carried out in NaOH/urea aqueous solution, under homogeneous conditions. The substitution degree of the prepared quaternized cellulose, cellulose-CHPTAC, increased with increasing molar ratio of CHPTAC/anhydroglucose unit (AGU), reaction temperature, and reaction time. The structure of the cellulose-CHPTAC was characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H- and 13C-NMR), and thermal gravimetric analysis (TGA). Moreover, a cellulose-CHPTAC sample (DS=0.52) was used to modify ground calcium carbonate (GCC) fillers by the surface wrapping method. The results showed that the filler retention was improved by surface modification of GCC fillers using cellulose-CHPTAC, and the negative impact of filler addition on paper strength was reduced. The quaternized cellulose prepared in NaOH/urea aqueous solution could be considered a new, promising filler modifier.