A composite comprised of dispersed conductive particles in an insulating polymer matrix is an excellent sensing material and could be used in flexible pressure sensors and tactile sensors. In this study, we investigated the variation of electrical resistance as a function of pressure for carbon black-silicone rubber composite. Samples were fabricated with different carbon black volume fractions. From experimental results, it was found that the composite has not only piezoresistivity but also electrical resistance creep behavior, which illustrates the relationship between electrical resistance and time. To describe and predict the above two phenomena, a mathematical model was established for particles filled polymer composites. When the piezoresistive composite was applied as a pressure-sensing unit, errors were seen due to "resistance creep" behavior. Based on this study, a method to inhibit such errors were investigated, developed, and realized.