Side-chain liquid crystal polymer (SCLCP)-silica composites were synthesized to enhance the electrorheological (ER) response by forming polar liquid crystal polymer-inorganic composites. Three types of SCLCP-silica composites were prepared to examine the effect of the aliphatic spacer length on the ER response of the composite suspensions. The SCLCPs consisted of a polymethacrylate backbone carrying cyanobiphenyl mesogenic groups as the side chains with various lengths of aliphatic spacer. The ER response increased with increasing electric field strength and decreasing aliphatic spacer length. The increasing ER response with decreasing spacer length was consistent with the behavior of the composite suspension dielectric properties. With the same spacer length, the ER response increased with increasing SCLCP/silica ratio.