In order to increase the dispersibility of MWNT in silica/PEG shear thickening fluid (STF), silica-coated MWNTs (Si-MWNTs) through covalent bonding were prepared and characterized. Amino group-introduced MWNT with a nitrogen atom content of 20 wt% was prepared first by reacting acid-treated MWNT and ethylene diamine, and then various amounts of silica were formed on the surface of MWNT initiated from the amino groups by using a sol-gel method. The silica formation on the MWNT surface was confirmed by FE-SEM, TEM, EA, and FTIR spectroscopy. When 3 wt% of pristine MWNT was added to the silica/PEG suspension, the shear thickening property was not observed and the MWNT was not dispersed well in the suspension. On the other hand, the suspension containing 3 wt% of Si-MWNT showed similar shear thickening behavior to that of simple silica/PEG. The critical shear-thickening point of silica/Si-MWNT suspension in PEG moved to a lower shear rate with increasing Si-MWNT content.