AbstractGround calcium carbonate (GCC) was modified with starch, sodium stearate, and sodium hexametaphosphate prior to the papermaking process. This paper is focused on the effect of shear on the modified GCC and considers the impact of adding modified GCC into paper. The coating efficiency of starch on GCC was investigated in terms of the shear-tolerance of the agglomerated filler. Experimental results showed that the precipitation temperature and the amount of crosslinking agent, sodium hexametaphosphate, both were important relative to shear tolerance. Lower precipitation temperature was beneficial for the starch coating. Within a certain range, more sodium hexametaphosphate led to a stronger complex. The results showed that 1.5% (based on MGCC) of sodium hexametaphosphate and a precipitation temperature of 60 °C were the optimum conditions for shear tolerance.