Microfibrillated cellulose (MFC) was first prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO) oxidation pretreatment and mechanical grinding in the presence of a certain amount of ground calcium carbonate (GCC). The effects of GCC dosage and grinding concentration on the fibrillation were investigated. The obtained MFC was then added to the bulk GCC to form MFC-modified GCC fillers. The properties of MFC-modified GCC fillers were compared to those of the traditional GCC fillers. Results showed that the resulting fibrils became more uniform when the dosage of GCC was 10%~15% and the concentration of the suspension was 6.97%. Compared to traditional GCC, the average particle size of the MFC-modified GCC fillers was larger. Scanning electron microscopy images showed that GCC and MFC formed a bridge structure in the MFC-modified GCC fillers. In the process of papermaking, the MFC-modified GCC fillers decreased the drainage rate but increased the retention of fillers. The prepared papers filled with MFC-modified GCC fillers had higher tensile strength than those filled with traditional GCC fillers.