Mid-infrared (MIR) fiber lasers have wide application prospects and great commercial value in the fields of medical operation, remote sensing and military weapon, etc. At present, Tm3+-doped glass can obtain broadband luminescence at 2m, the introduction of Ho3+ or Er3+ ions also shows a tunable MIR emission but with limited success. Herein, the rare-earth (RE) doped glass with quantum dots (QDs) precipitation is proposed for achieving ultra-broadband MIR emissions. The types and sizes of QDs are determined by the XRD and TEM, and their optical properties are further characterized by the absorption and emission spectra as well as the lifetime decay curves. It is found that the diameter of the QDs is gradually increased from 1.7 to 5.1nm by increasing the heat-treated temperature from 490 degrees C to 530 degrees C, respectively. Interestingly, an ultra-broadband emission covering 1400-2600nm is achieved from the heat-treated glass upon the excitation of 808nm laser diode as a result of an overlapped emission from Tm3+ and PbS. All results suggest that these QDs-precipitated RE-doped glasses have important application prospects in ultra-broadband MIR laser glass, glass fiber, and fiber lasers.