The Sn-doped CsPbBr₃ quantum dots were synthesized by the hot injection method in this paper. The transmission electron microscope (TEM) and X-ray diffractometer (XRD) characterization results show that doping with a small amount of Sn can partially replace Pb and passivate the CsPbBr₃ quantum dots, reducing the surface defects of quantum dots and improving the photoluminescence quantum yield (PLQY) of the quantum dots. Specifically, in the case of n_Pb∶n_Sn=9∶1, the PLQY of the quantum dots is increased from 21.0% of the undoped CsPbBr₃ quantum dots to 40.4% of the Sn-doped ones. However, with the rise in Sn content, some heterogeneous phases appear in the XRD patterns, the photoluminescene weakens, and the PLQY decreases from 40.4% of small amount of Sn-doped (n_Pb∶n_Sn=9∶1) quantum dots to 10.4% of CsPb_0.6Sn_0.4Br₃ quantum dots. In conclusion, CsPb_0.9Sn_0.1Br₃ doped with a small amount Sn has the strongest photoluminescence and electroluminescence, with a photoluminescence peak at 511 nm, a PLQY of 40.4%, an electroluminescence peak at 512 nm, and an electroluminescence brightness of 343.0 cd/m ² which is 2.5 times that of the undoped CsPbBr₃ quantum dots. The experiments in this paper demonstrate that doping CsPbBr₃ with a small amount of Sn (CsPb_0.9Sn_0.1Br₃) can decrease the surface defects of quantum dots and improve the photoluminescence and electroluminescence properties of the quantum dots.