In this study, we had investigated the amplified spontaneous emission (ASE) characteristics of CdSe/ZnS quantum dot (QDs) in a colloidal liquid. A third harmonic of Nd:YAG laser (355 nm) was used to produce laser-induced fluorescence (LIF) at 605 nm with a spectral width of 0 nm [full width at half maximum (FWHM)]. When the pump power and focusing were carefully optimized, an ASE at 610 nm with a spectral width of Δλ = 8 nm (FWHM) could be obtained. The beam was directional with a divergence of 10 milli radians (mrad); but the conversion efficiency was about 0.05%.