In this paper, CsPbBr3 perovskite QDs (quantum dots) were synthesized by supersaturated recrystallization method. The process of synthesis of CsPbBr3 QDs by supersaturated recrystallization method optimized by HBr was explored. The surface defects of QDs were reduced, and the luminescent properties were improved. The PLQY (photo luminescence quantum yield) of CsPbBr3 QDs was increased from 45 to 95%. The influence factors of HBr post-treatment were studied. The results showed that the optimal temperature of post-treatment was 20 ℃, and the optimal amount of HBr was 20 μ L.