High temperature vulcanized silicone rubber (SR) based nanocomposites with carbon black (CB) and ionic liquid-modified carbon black (CB-IL) as fillers were fabricated using mechanical mixing method and their piezoresistive properties were carefully characterized. 1-hexadecyl-3-methylimidazolium bromide (IL) can improve the dispersibility of CB in SR matrix by morphology characterization. The CB-IL/SR composites showed a lower percolation threshold compared with CB/SR composites. The CB-IL/SR composite with 5vol% content of CB-IL shows higher piezoresistivity, better repeatability and shorter relaxation time due to the plasticizing effect of IL. The results suggest that the CB-IL/SR composites provide a new route toward fabrication of flexible piezoresistive sensors and wearable electronic devices.