Based on the optical trapping micro-and nano-particles effect of the evanescent field, we propose to investigate the optical trapping technique for semiconductor quantum dots by using tapered optical fiber. With the laser at 980 nm wavelength as light source, the PbS quantum dots (QDs) are absorbed and deposited on the surface of the tapered fiber successfully. By optical pumping, the photoluminescence from the tapered fiber after trapping PbS QDs is observed, and a gain of 6.8 dB is obtained at 1550 nm wavelength band.