Perovskite-based blue light-emitting particles have received considerable attention to address manufacturing difficulties and defect occurrence due to wide band-gap compared to red and green materials. Cs-based perovskite quantum dots (QDs) mainly require preparing Cs-oleates to obtain QDs. However, we would like to propose a facile one-pot method to synthesize CsPbClBr2 blue-emitting QDs. We investigated the precursor ratio and suitable solvent for precursor dissolution. In the case of non-stoichiometric precursor ratios, additional products coexisted in the process of obtaining CsPbClBr2. The CsPbClBr2 QDs obtained using a stoichiometric precursor showed superior optical properties with a QY of 70.55%, and maintained high PL intensity with no discoloration observed for 400 h. Additionally, when deionized water was added to form a double layer with a hexane layer, the light emitting was maintained for 15 days. Based on these result, the suggested one-pot synthesis for QDs presents a simple and facile method to synthesize blue-emitting materials.