Abstract: The piezoresistivity of high density polyethylene/graphite (HDPE/GP) semiconductive composites was studied through measuring the resistance change under uniaxial pressure. The results show that there exists a marking pressure dependence of the conductivity in HDPE/GP composites, in which the socalled negative pressure coefficient of resistive ( NPCR )and positive pressure coefficient of resistive ( PPCR ) are observed under minute and moderate pressures. Under constant pressures, timedependent resistivity is an outstanding characteristic for the composites, which is defined as resistance creep. The breakdown and rebuildup process of conductive network under pressure may be responsible for the pressureand timedependence of resistivity.