We report an approach to achieving a tunable time response of the nonlinearity of nano-Ag:polymer nanocomposites. The response time of the nonlinearity of the nanocomposite made of Ag nanoparticles dispersed in poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] matrix can be tuned by adjusting the doping concentration of CdTe(0.13)S(0.87) quantum dots. An ultrafast response time of 14.5 ps is achieved for a doping concentration of 27%. Moreover, the third-order nonlinear susceptibility, achieving the order of 10(-5) esu, is one order of magnitude larger than that of the undoped nanocomposite. An ultrafast and low-power photonic crystal all-optical switching is also realized based on the photonic bandgap shift.